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Use percpu_counter for obj_alloc counter of Linux-backed caches

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A previous commit enabled the tracking of object allocations
in Linux-backed caches from the SPL layer for debuggability.
The commit is: 9a170fc6fe54f1e852b6c39630fe5ef2bbd97c16

Unfortunately, it also introduced minor performance regressions
that were highlighted by the ZFS perf test-suite. Within Delphix
we found that the regression would be from -1%, all the way up
to -8% for some workloads.

This commit brings performance back up to par by creating a
separate counter for those caches and making it a percpu in
order to avoid lock-contention.

The initial performance testing was done by myself, and the
final round was conducted by @tonynguien who was also the one
that discovered the regression and highlighted the culprit.

Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Closes #10397
This commit is contained in:
Serapheim Dimitropoulos
2020-06-26 18:06:50 -07:00
committed by GitHub
parent 7b232e9354
commit ec1fea4516
7 changed files with 100 additions and 8 deletions
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config/kernel-percpu.m4
+34
View File
@@ -0,0 +1,34 @@
dnl #
dnl # 3.18 API change,
dnl # The function percpu_counter_init now must be passed a GFP mask.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_PERCPU_COUNTER_INIT], [
ZFS_LINUX_TEST_SRC([percpu_counter_init_with_gfp], [
#include <linux/gfp.h>
#include <linux/percpu_counter.h>
],[
struct percpu_counter counter;
int error;
error = percpu_counter_init(&counter, 0, GFP_KERNEL);
])
])
AC_DEFUN([ZFS_AC_KERNEL_PERCPU_COUNTER_INIT], [
AC_MSG_CHECKING([whether percpu_counter_init() wants gfp_t])
ZFS_LINUX_TEST_RESULT([percpu_counter_init_with_gfp], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_PERCPU_COUNTER_INIT_WITH_GFP, 1,
[percpu_counter_init() wants gfp_t])
],[
AC_MSG_RESULT(no)
])
])
AC_DEFUN([ZFS_AC_KERNEL_SRC_PERCPU], [
ZFS_AC_KERNEL_SRC_PERCPU_COUNTER_INIT
])
AC_DEFUN([ZFS_AC_KERNEL_PERCPU], [
ZFS_AC_KERNEL_PERCPU_COUNTER_INIT
])