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Date:      Tue, 28 Aug 2018 11:05:43 +0200
From:      Yamagi Burmeister <lists@yamagi.org>
To:        lev@FreeBSD.org
Cc:        freebsd-fs@freebsd.org, MacCrest@gmail.com
Subject:   Re: ZFS (ARC) performance regression in r321610
Message-ID:  <20180828110543.7cc7fa65a0e04e29a06a32b1@yamagi.org>
In-Reply-To: <20180828105048.d5a4133c8a932eff900bd758@yamagi.org>
References:  <20180827154727.80f92fff9bbc931b37928d43@yamagi.org> <3c6f8c96-6ac9-7257-c8c0-8be2063a7c19@FreeBSD.org> <20180827182723.cd8ec6bac6448793b25ef91c@yamagi.org> <20180828105048.d5a4133c8a932eff900bd758@yamagi.org>

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On Tue, 28 Aug 2018 10:50:48 +0200
Yamagi Burmeister <lists@yamagi.org> wrote:

> ZFS on Linux exposes zfs_abd_scatter_enabled through a module
> parameter. What about turning it into a sysctl? Something like this:

Ups, there sneaked an unrelated edit into the patch. New version here:

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c b/sys/cdd=
l/contrib/opensolaris/uts/common/fs/zfs/abd.c
index 2cd87c2b87b..5de74ef3325 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c
@@ -140,6 +140,13 @@ static abd_stats_t abd_stats =3D {
  */
 boolean_t zfs_abd_scatter_enabled =3D B_TRUE;
=20
+#if defined(__FreeBSD__) && defined(_KERNEL)
+SYSCTL_DECL(_vfs_zfs);
+
+SYSCTL_UINT(_vfs_zfs, OID_AUTO, abd_scatter_enabled, CTLFLAG_RWTUN,
+    &zfs_abd_scatter_enabled, 1, "Make all future ABDs linear");
+#endif
+
 /*
  * The size of the chunks ABD allocates. Because the sizes allocated from =
the
  * kmem_cache can't change, this tunable can only be modified at boot. Cha=
nging
@@ -151,8 +158,6 @@ boolean_t zfs_abd_scatter_enabled =3D B_TRUE;
 size_t zfs_abd_chunk_size =3D 4096;
=20
 #if defined(__FreeBSD__) && defined(_KERNEL)
-SYSCTL_DECL(_vfs_zfs);
-
 SYSCTL_ULONG(_vfs_zfs, OID_AUTO, abd_chunk_size, CTLFLAG_RDTUN,
     &zfs_abd_chunk_size, 0, "The size of the chunks ABD allocates");
 #endif


--=20
Homepage: https://www.yamagi.org
Github:   https://github.com/yamagi
GPG:      0x1D502515

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