From patchwork Wed Jul 29 08:10:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 276698 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00, DATE_IN_PAST_96_XX, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 781A3C433DF for ; Wed, 12 Aug 2020 12:43:18 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 410332080C for ; Wed, 12 Aug 2020 12:43:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="oPvqrIbv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 410332080C Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=crudebyte.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45694 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k5q69-0003V9-GK for qemu-devel@archiver.kernel.org; Wed, 12 Aug 2020 08:43:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33898) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <46488b627ac8f13a3cbf83cfbfa011e82314b279@lizzy.crudebyte.com>) id 1k5q3j-0000Mh-4u for qemu-devel@nongnu.org; Wed, 12 Aug 2020 08:40:47 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:36499) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <46488b627ac8f13a3cbf83cfbfa011e82314b279@lizzy.crudebyte.com>) id 1k5q3g-0004tq-VU for qemu-devel@nongnu.org; Wed, 12 Aug 2020 08:40:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:References:In-Reply-To: Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Content-ID: Content-Description; bh=RLW7R/RLw3j8fw80S3T+y1rUBTLcRUwqCiVI6RAC/V4=; b=oPvqr Ibvj0V5AOo6mG50FQSOcaPeVz7nBfPArR7D84TLmHQyDs0ZdakTIlrIGENYCmGfhuEi0xnYg6qC0w eQQveuwNXTRD31adgw+m4eLh7ZO3/e2buoGNZKO8n3q5MHKWW0MqmA3bhKSapzZNmufu7VejM8oo/ wwIWzoBRZKkHQ8XKJgeKA+4ZWLhuc/2nU4sPU2Bk9R/JrFVWpCtACOd5ZfbcEZHz4R9E4I/fG1jKo wEkCZBK50LpKuHpLSDCyFt2PQhyK1EfIDHn9+RflzNqK6/vJI7Bf4+T5GW/RtrhEVupwYDbQr1csL sK4/+XZskdzXV/A+5kCAaXo67gnUA==; Message-Id: <46488b627ac8f13a3cbf83cfbfa011e82314b279.1597226797.git.qemu_oss@crudebyte.com> In-Reply-To: References: From: Christian Schoenebeck Date: Wed, 29 Jul 2020 10:10:23 +0200 Subject: [PULL 1/7] tests/virtio-9p: added split readdir tests To: qemu-devel@nongnu.org, Peter Maydell Cc: Greg Kurz Received-SPF: none client-ip=91.194.90.13; envelope-from=46488b627ac8f13a3cbf83cfbfa011e82314b279@lizzy.crudebyte.com; helo=lizzy.crudebyte.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/12 08:16:56 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: 13 X-Spam_score: 1.3 X-Spam_bar: + X-Spam_report: (1.3 / 5.0 requ) BAYES_00=-1.9, DATE_IN_PAST_96_XX=3.405, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_NONE=0.001, URIBL_BLOCKED=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The previous, already existing 'basic' readdir test simply used a 'count' parameter big enough to retrieve all directory entries with a single Treaddir request. In the 3 new 'split' readdir tests added by this patch, directory entries are retrieved, split over several Treaddir requests by picking small 'count' parameters which force the server to truncate the response. So the test client sends as many Treaddir requests as necessary to get all directory entries. The following 3 new tests are added (executed in this sequence): 1. Split readdir test with count=512 2. Split readdir test with count=256 3. Split readdir test with count=128 This test case sequence is chosen because the smaller the 'count' value, the higher the chance of errors in case of implementation bugs on server side. Signed-off-by: Christian Schoenebeck Reviewed-by: Greg Kurz Message-Id: <569b2e05ab1d0223b14a12dfbdf3ad5e8b3ac131.1596012787.git.qemu_oss@crudebyte.com> Signed-off-by: Christian Schoenebeck --- tests/qtest/virtio-9p-test.c | 108 +++++++++++++++++++++++++++++++++++ 1 file changed, 108 insertions(+) diff --git a/tests/qtest/virtio-9p-test.c b/tests/qtest/virtio-9p-test.c index 2167322985..de30b717b6 100644 --- a/tests/qtest/virtio-9p-test.c +++ b/tests/qtest/virtio-9p-test.c @@ -578,6 +578,7 @@ static bool fs_dirents_contain_name(struct V9fsDirent *e, const char* name) return false; } +/* basic readdir test where reply fits into a single response message */ static void fs_readdir(void *obj, void *data, QGuestAllocator *t_alloc) { QVirtio9P *v9p = obj; @@ -631,6 +632,89 @@ static void fs_readdir(void *obj, void *data, QGuestAllocator *t_alloc) g_free(wnames[0]); } +/* readdir test where overall request is split over several messages */ +static void fs_readdir_split(void *obj, void *data, QGuestAllocator *t_alloc, + uint32_t count) +{ + QVirtio9P *v9p = obj; + alloc = t_alloc; + char *const wnames[] = { g_strdup(QTEST_V9FS_SYNTH_READDIR_DIR) }; + uint16_t nqid; + v9fs_qid qid; + uint32_t nentries, npartialentries; + struct V9fsDirent *entries, *tail, *partialentries; + P9Req *req; + int fid; + uint64_t offset; + + fs_attach(v9p, NULL, t_alloc); + + fid = 1; + offset = 0; + entries = NULL; + nentries = 0; + tail = NULL; + + req = v9fs_twalk(v9p, 0, fid, 1, wnames, 0); + v9fs_req_wait_for_reply(req, NULL); + v9fs_rwalk(req, &nqid, NULL); + g_assert_cmpint(nqid, ==, 1); + + req = v9fs_tlopen(v9p, fid, O_DIRECTORY, 0); + v9fs_req_wait_for_reply(req, NULL); + v9fs_rlopen(req, &qid, NULL); + + /* + * send as many Treaddir requests as required to get all directory + * entries + */ + while (true) { + npartialentries = 0; + partialentries = NULL; + + req = v9fs_treaddir(v9p, fid, offset, count, 0); + v9fs_req_wait_for_reply(req, NULL); + v9fs_rreaddir(req, &count, &npartialentries, &partialentries); + if (npartialentries > 0 && partialentries) { + if (!entries) { + entries = partialentries; + nentries = npartialentries; + tail = partialentries; + } else { + tail->next = partialentries; + nentries += npartialentries; + } + while (tail->next) { + tail = tail->next; + } + offset = tail->offset; + } else { + break; + } + } + + g_assert_cmpint( + nentries, ==, + QTEST_V9FS_SYNTH_READDIR_NFILES + 2 /* "." and ".." */ + ); + + /* + * Check all file names exist in returned entries, ignore their order + * though. + */ + g_assert_cmpint(fs_dirents_contain_name(entries, "."), ==, true); + g_assert_cmpint(fs_dirents_contain_name(entries, ".."), ==, true); + for (int i = 0; i < QTEST_V9FS_SYNTH_READDIR_NFILES; ++i) { + char *name = g_strdup_printf(QTEST_V9FS_SYNTH_READDIR_FILE, i); + g_assert_cmpint(fs_dirents_contain_name(entries, name), ==, true); + g_free(name); + } + + v9fs_free_dirents(entries); + + g_free(wnames[0]); +} + static void fs_walk_no_slash(void *obj, void *data, QGuestAllocator *t_alloc) { QVirtio9P *v9p = obj; @@ -793,6 +877,24 @@ static void fs_flush_ignored(void *obj, void *data, QGuestAllocator *t_alloc) g_free(wnames[0]); } +static void fs_readdir_split_128(void *obj, void *data, + QGuestAllocator *t_alloc) +{ + fs_readdir_split(obj, data, t_alloc, 128); +} + +static void fs_readdir_split_256(void *obj, void *data, + QGuestAllocator *t_alloc) +{ + fs_readdir_split(obj, data, t_alloc, 256); +} + +static void fs_readdir_split_512(void *obj, void *data, + QGuestAllocator *t_alloc) +{ + fs_readdir_split(obj, data, t_alloc, 512); +} + static void register_virtio_9p_test(void) { qos_add_test("config", "virtio-9p", pci_config, NULL); @@ -810,6 +912,12 @@ static void register_virtio_9p_test(void) qos_add_test("fs/flush/ignored", "virtio-9p", fs_flush_ignored, NULL); qos_add_test("fs/readdir/basic", "virtio-9p", fs_readdir, NULL); + qos_add_test("fs/readdir/split_512", "virtio-9p", + fs_readdir_split_512, NULL); + qos_add_test("fs/readdir/split_256", "virtio-9p", + fs_readdir_split_256, NULL); + qos_add_test("fs/readdir/split_128", "virtio-9p", + fs_readdir_split_128, NULL); } libqos_init(register_virtio_9p_test); From patchwork Wed Jul 29 08:13:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 276696 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00, DATE_IN_PAST_96_XX, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9A1AC433E0 for ; Wed, 12 Aug 2020 12:50:57 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7541620774 for ; Wed, 12 Aug 2020 12:50:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="eEGFsNTN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7541620774 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=crudebyte.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45686 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k5qDY-0006fj-OD for qemu-devel@archiver.kernel.org; Wed, 12 Aug 2020 08:50:56 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35782) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <0c4356ba7dafc8ecb5877a42fc0d68d45ccf5951@lizzy.crudebyte.com>) id 1k5q9n-0001FH-QL for qemu-devel@nongnu.org; Wed, 12 Aug 2020 08:47:03 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:39267) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <0c4356ba7dafc8ecb5877a42fc0d68d45ccf5951@lizzy.crudebyte.com>) id 1k5q9m-0005yi-4e for qemu-devel@nongnu.org; Wed, 12 Aug 2020 08:47:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:References:In-Reply-To: Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Content-ID: Content-Description; bh=GNy1vJScIjnAUJYX0AIEa090ls86NMVH10hGMsFeWbM=; b=eEGFs NTNVXUXSYhHiV5v5ReeEriH5dNc2X2+4RcjC/HE8ymqJ/xO2e6gAGLO6Tn71TrtLca/I8oRuNUSl7 Fw2BFpI6CCKo+vDwXmmiPR+HZRI0Zi8iAAcmMuCoCNYxlAZ42f0hCZdUZVG1/yKesFlmpJxtg+dtp QP7ImQNkEZ3/m38mXPPK9Y1VI2RPg0eWfYeRXQUMlaJlTovtMeKpdGu6fwhj6N5Uf1mhUk3wu87f+ bh9Em6+fCvrs2fo8ovuRQ1R20XedryKLTtsWUHcDHeFIK48y/NGWtyS1tFN1yXJAhmNNLxeqbiZXb 0hcM71ggTTzwYZWEoGZ9gc/gsY2IA==; Message-Id: <0c4356ba7dafc8ecb5877a42fc0d68d45ccf5951.1597226797.git.qemu_oss@crudebyte.com> In-Reply-To: References: From: Christian Schoenebeck Date: Wed, 29 Jul 2020 10:13:05 +0200 Subject: [PULL 5/7] 9pfs: T_readdir latency optimization To: qemu-devel@nongnu.org, Peter Maydell Cc: Greg Kurz Received-SPF: none client-ip=91.194.90.13; envelope-from=0c4356ba7dafc8ecb5877a42fc0d68d45ccf5951@lizzy.crudebyte.com; helo=lizzy.crudebyte.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/12 08:16:56 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: 13 X-Spam_score: 1.3 X-Spam_bar: + X-Spam_report: (1.3 / 5.0 requ) BAYES_00=-1.9, DATE_IN_PAST_96_XX=3.405, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_NONE=0.001, URIBL_BLOCKED=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Make top half really top half and bottom half really bottom half: Each T_readdir request handling is hopping between threads (main I/O thread and background I/O driver threads) several times for every individual directory entry, which sums up to huge latencies for handling just a single T_readdir request. Instead of doing that, collect now all required directory entries (including all potentially required stat buffers for each entry) in one rush on a background I/O thread from fs driver by calling the previously added function v9fs_co_readdir_many() instead of v9fs_co_readdir(), then assemble the entire resulting network response message for the readdir request on main I/O thread. The fs driver is still aborting the directory entry retrieval loop (on the background I/O thread inside of v9fs_co_readdir_many()) as soon as it would exceed the client's requested maximum R_readdir response size. So this will not introduce a performance penalty on another end. Also: No longer seek initial directory position in v9fs_readdir(), as this is now handled (more consistently) by v9fs_co_readdir_many() instead. Signed-off-by: Christian Schoenebeck Message-Id: Signed-off-by: Christian Schoenebeck --- hw/9pfs/9p.c | 132 ++++++++++++++++++++++----------------------------- 1 file changed, 58 insertions(+), 74 deletions(-) diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 7a228c4828..cc4094b971 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -972,30 +972,6 @@ static int coroutine_fn fid_to_qid(V9fsPDU *pdu, V9fsFidState *fidp, return 0; } -static int coroutine_fn dirent_to_qid(V9fsPDU *pdu, V9fsFidState *fidp, - struct dirent *dent, V9fsQID *qidp) -{ - struct stat stbuf; - V9fsPath path; - int err; - - v9fs_path_init(&path); - - err = v9fs_co_name_to_path(pdu, &fidp->path, dent->d_name, &path); - if (err < 0) { - goto out; - } - err = v9fs_co_lstat(pdu, &path, &stbuf); - if (err < 0) { - goto out; - } - err = stat_to_qid(pdu, &stbuf, qidp); - -out: - v9fs_path_free(&path); - return err; -} - V9fsPDU *pdu_alloc(V9fsState *s) { V9fsPDU *pdu = NULL; @@ -2328,62 +2304,74 @@ size_t v9fs_readdir_response_size(V9fsString *name) return 24 + v9fs_string_size(name); } +static void v9fs_free_dirents(struct V9fsDirEnt *e) +{ + struct V9fsDirEnt *next = NULL; + + for (; e; e = next) { + next = e->next; + g_free(e->dent); + g_free(e->st); + g_free(e); + } +} + static int coroutine_fn v9fs_do_readdir(V9fsPDU *pdu, V9fsFidState *fidp, - int32_t max_count) + off_t offset, int32_t max_count) { size_t size; V9fsQID qid; V9fsString name; int len, err = 0; int32_t count = 0; - off_t saved_dir_pos; struct dirent *dent; + struct stat *st; + struct V9fsDirEnt *entries = NULL; - /* save the directory position */ - saved_dir_pos = v9fs_co_telldir(pdu, fidp); - if (saved_dir_pos < 0) { - return saved_dir_pos; - } - - while (1) { - v9fs_readdir_lock(&fidp->fs.dir); + /* + * inode remapping requires the device id, which in turn might be + * different for different directory entries, so if inode remapping is + * enabled we have to make a full stat for each directory entry + */ + const bool dostat = pdu->s->ctx.export_flags & V9FS_REMAP_INODES; - err = v9fs_co_readdir(pdu, fidp, &dent); - if (err || !dent) { - break; - } - v9fs_string_init(&name); - v9fs_string_sprintf(&name, "%s", dent->d_name); - if ((count + v9fs_readdir_response_size(&name)) > max_count) { - v9fs_readdir_unlock(&fidp->fs.dir); + /* + * Fetch all required directory entries altogether on a background IO + * thread from fs driver. We don't want to do that for each entry + * individually, because hopping between threads (this main IO thread + * and background IO driver thread) would sum up to huge latencies. + */ + count = v9fs_co_readdir_many(pdu, fidp, &entries, offset, max_count, + dostat); + if (count < 0) { + err = count; + count = 0; + goto out; + } + count = 0; - /* Ran out of buffer. Set dir back to old position and return */ - v9fs_co_seekdir(pdu, fidp, saved_dir_pos); - v9fs_string_free(&name); - return count; - } + for (struct V9fsDirEnt *e = entries; e; e = e->next) { + dent = e->dent; if (pdu->s->ctx.export_flags & V9FS_REMAP_INODES) { - /* - * dirent_to_qid() implies expensive stat call for each entry, - * we must do that here though since inode remapping requires - * the device id, which in turn might be different for - * different entries; we cannot make any assumption to avoid - * that here. - */ - err = dirent_to_qid(pdu, fidp, dent, &qid); + st = e->st; + /* e->st should never be NULL, but just to be sure */ + if (!st) { + err = -1; + break; + } + + /* remap inode */ + err = stat_to_qid(pdu, st, &qid); if (err < 0) { - v9fs_readdir_unlock(&fidp->fs.dir); - v9fs_co_seekdir(pdu, fidp, saved_dir_pos); - v9fs_string_free(&name); - return err; + break; } } else { /* * Fill up just the path field of qid because the client uses * only that. To fill the entire qid structure we will have * to stat each dirent found, which is expensive. For the - * latter reason we don't call dirent_to_qid() here. Only drawback + * latter reason we don't call stat_to_qid() here. Only drawback * is that no multi-device export detection of stat_to_qid() * would be done and provided as error to the user here. But * user would get that error anyway when accessing those @@ -2396,25 +2384,26 @@ static int coroutine_fn v9fs_do_readdir(V9fsPDU *pdu, V9fsFidState *fidp, qid.version = 0; } + v9fs_string_init(&name); + v9fs_string_sprintf(&name, "%s", dent->d_name); + /* 11 = 7 + 4 (7 = start offset, 4 = space for storing count) */ len = pdu_marshal(pdu, 11 + count, "Qqbs", &qid, dent->d_off, dent->d_type, &name); - v9fs_readdir_unlock(&fidp->fs.dir); + v9fs_string_free(&name); if (len < 0) { - v9fs_co_seekdir(pdu, fidp, saved_dir_pos); - v9fs_string_free(&name); - return len; + err = len; + break; } + count += len; - v9fs_string_free(&name); - saved_dir_pos = dent->d_off; } - v9fs_readdir_unlock(&fidp->fs.dir); - +out: + v9fs_free_dirents(entries); if (err < 0) { return err; } @@ -2457,12 +2446,7 @@ static void coroutine_fn v9fs_readdir(void *opaque) retval = -EINVAL; goto out; } - if (initial_offset == 0) { - v9fs_co_rewinddir(pdu, fidp); - } else { - v9fs_co_seekdir(pdu, fidp, initial_offset); - } - count = v9fs_do_readdir(pdu, fidp, max_count); + count = v9fs_do_readdir(pdu, fidp, (off_t) initial_offset, max_count); if (count < 0) { retval = count; goto out; From patchwork Wed Jul 29 08:42:28 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 276697 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00, DATE_IN_PAST_96_XX, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 287A8C433E0 for ; Wed, 12 Aug 2020 12:47:10 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E8CBE207F7 for ; 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Wed, 12 Aug 2020 08:46:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:References:In-Reply-To: Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Content-ID: Content-Description; bh=iIOY7lnyCREAN0i5cfmgv+fsotclpHEmOG5eXJ6R0b4=; b=bUaJf QqLeGuM9Nl6kcIvVz0EEH5Oa0xRx+FlHzuB9DFykCI4ANl5Uvsa73OSIjgwfzvT3ZjwH37R0XjZHJ Lnv/kP2hHWh6fn2Cm8J2owNIRQZNMJl800RtiTUSP2DKq1w5O7m3eXCohEiIVI0i0QYlHDFXaTazo /kRqFBTh+MAHE81gSNgFW87uyIm5ybsd/ZwwYrbOYR9Gw+jeeO8egdhFhXSyuTi3P1VzXPocia8xU t+kjAGG2Hq6x18AWCrSLVslOAIXzfvj8ihdleTcuKipmE1iX4iU5W5Tq+QYBuTIvB9WuyXOz/7MHb l1wuu9xx1N+u+eXSdpN8O63AThyxQ==; Message-Id: In-Reply-To: References: From: Christian Schoenebeck Date: Wed, 29 Jul 2020 10:42:28 +0200 Subject: [PULL 7/7] 9pfs: clarify latency of v9fs_co_run_in_worker() To: qemu-devel@nongnu.org, Peter Maydell Cc: Greg Kurz Received-SPF: none client-ip=91.194.90.13; envelope-from=da9f2eda2551c1cbd98f72730e5b754f2149a85c@lizzy.crudebyte.com; helo=lizzy.crudebyte.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/12 08:16:56 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: 13 X-Spam_score: 1.3 X-Spam_bar: + X-Spam_report: (1.3 / 5.0 requ) BAYES_00=-1.9, DATE_IN_PAST_96_XX=3.405, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_NONE=0.001, URIBL_BLOCKED=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" As we just fixed a severe performance issue with Treaddir request handling, clarify this overall issue as a comment on v9fs_co_run_in_worker() with the intention to hopefully prevent such performance mistakes in future (and fixing other yet outstanding ones). Signed-off-by: Christian Schoenebeck Message-Id: <4d34d332e1aaa8a2cf8dc0b5da4fd7727f2a86e8.1596012787.git.qemu_oss@crudebyte.com> Signed-off-by: Christian Schoenebeck --- hw/9pfs/coth.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/hw/9pfs/coth.h b/hw/9pfs/coth.h index fd4a45bc7c..c51289903d 100644 --- a/hw/9pfs/coth.h +++ b/hw/9pfs/coth.h @@ -19,7 +19,7 @@ #include "qemu/coroutine.h" #include "9p.h" -/* +/** * we want to use bottom half because we want to make sure the below * sequence of events. * @@ -28,6 +28,16 @@ * 3. Enter the coroutine in the worker thread. * we cannot swap step 1 and 2, because that would imply worker thread * can enter coroutine while step1 is still running + * + * @b PERFORMANCE @b CONSIDERATIONS: As a rule of thumb, keep in mind + * that hopping between threads adds @b latency! So when handling a + * 9pfs request, avoid calling v9fs_co_run_in_worker() too often, because + * this might otherwise sum up to a significant, huge overall latency for + * providing the response for just a single request. For that reason it + * is highly recommended to fetch all data from fs driver with a single + * fs driver request on a background I/O thread (bottom half) in one rush + * first and then eventually assembling the final response from that data + * on main I/O thread (top half). */ #define v9fs_co_run_in_worker(code_block) \ do { \