87 lines
2.8 KiB
Diff
87 lines
2.8 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Alexander Motin <mav@FreeBSD.org>
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Date: Mon, 20 Nov 2017 19:56:01 +0200
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Subject: [PATCH] OpenZFS 8835 - Speculative prefetch in ZFS not working for
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misaligned reads
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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In case of misaligned I/O sequential requests are not detected as such
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due to overlaps in logical block sequence:
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dmu_zfetch(fffff80198dd0ae0, 27347, 9, 1)
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dmu_zfetch(fffff80198dd0ae0, 27355, 9, 1)
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dmu_zfetch(fffff80198dd0ae0, 27363, 9, 1)
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dmu_zfetch(fffff80198dd0ae0, 27371, 9, 1)
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dmu_zfetch(fffff80198dd0ae0, 27379, 9, 1)
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dmu_zfetch(fffff80198dd0ae0, 27387, 9, 1)
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This patch makes single block overlap to be counted as a stream hit,
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improving performance up to several times.
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Authored by: Alexander Motin <mav@FreeBSD.org>
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Approved by: Gordon Ross <gwr@nexenta.com>
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Reviewed by: Matthew Ahrens <mahrens@delphix.com>
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Reviewed by: Allan Jude <allanjude@freebsd.org>
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Reviewed by: Gvozden Neskovic <neskovic@gmail.com>
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Reviewed by: George Melikov <mail@gmelikov.ru>
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Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
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OpenZFS-issue: https://www.illumos.org/issues/8835
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OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aab6dd482a
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Closes #7062
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(cherry picked from commit 701ebd014af3a0c7485056d8c96ecfb379867fd8)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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module/zfs/dmu_zfetch.c | 24 +++++++++++++++++++-----
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1 file changed, 19 insertions(+), 5 deletions(-)
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diff --git a/module/zfs/dmu_zfetch.c b/module/zfs/dmu_zfetch.c
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index 1bf5c4e34..e72e9ef9c 100644
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--- a/module/zfs/dmu_zfetch.c
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+++ b/module/zfs/dmu_zfetch.c
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@@ -228,19 +228,33 @@ dmu_zfetch(zfetch_t *zf, uint64_t blkid, uint64_t nblks, boolean_t fetch_data)
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rw_enter(&zf->zf_rwlock, RW_READER);
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+ /*
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+ * Find matching prefetch stream. Depending on whether the accesses
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+ * are block-aligned, first block of the new access may either follow
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+ * the last block of the previous access, or be equal to it.
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+ */
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for (zs = list_head(&zf->zf_stream); zs != NULL;
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zs = list_next(&zf->zf_stream, zs)) {
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- if (blkid == zs->zs_blkid) {
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+ if (blkid == zs->zs_blkid || blkid + 1 == zs->zs_blkid) {
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mutex_enter(&zs->zs_lock);
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/*
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* zs_blkid could have changed before we
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* acquired zs_lock; re-check them here.
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*/
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- if (blkid != zs->zs_blkid) {
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- mutex_exit(&zs->zs_lock);
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- continue;
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+ if (blkid == zs->zs_blkid) {
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+ break;
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+ } else if (blkid + 1 == zs->zs_blkid) {
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+ blkid++;
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+ nblks--;
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+ if (nblks == 0) {
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+ /* Already prefetched this before. */
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+ mutex_exit(&zs->zs_lock);
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+ rw_exit(&zf->zf_rwlock);
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+ return;
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+ }
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+ break;
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}
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- break;
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+ mutex_exit(&zs->zs_lock);
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}
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}
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--
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2.14.2
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