xfs: only run xfs_error_test if error injection is active (c76febef) · Commits · 戴 / test

Recent tests writing lots of small files showed the flusher thread being CPU bound and taking a long time to do allocations on a debug kernel. perf showed this as the prime reason: samples pcnt function DSO _______ _____ ___________________________ _________________ 224648.00 36.8% xfs_error_test [kernel.kallsyms] 86045.00 14.1% xfs_btree_check_sblock [kernel.kallsyms] 39778.00 6.5% prandom32 [kernel.kallsyms] 37436.00 6.1% xfs_btree_increment [kernel.kallsyms] 29278.00 4.8% xfs_btree_get_rec [kernel.kallsyms] 27717.00 4.5% random32 [kernel.kallsyms] Walking btree blocks during allocation checking them requires each block (a cache hit, so no I/O) call xfs_error_test(), which then does a random32() call as the first operation. IOWs, ~50% of the CPU is being consumed just testing whether we need to inject an error, even though error injection is not active. Kill this overhead when error injection is not active by adding a global counter of active error traps and only calling into xfs_error_test when fault injection is active. Signed-off-by:

Dave Chinner <dchinner@redhat.com> Reviewed-by:

Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_error.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -58,6 +58,7 @@ xfs_error_trap(int e)
		int xfs_etest[XFS_NUM_INJECT_ERROR];
		int64_t xfs_etest_fsid[XFS_NUM_INJECT_ERROR];
		char * xfs_etest_fsname[XFS_NUM_INJECT_ERROR];
		int xfs_error_test_active;

		int
		xfs_error_test(int error_tag, int fsidp, char expression,
		@@ -108,6 +109,7 @@ xfs_errortag_add(int error_tag, xfs_mount_t *mp)
		len = strlen(mp->m_fsname);
		xfs_etest_fsname[i] = kmem_alloc(len + 1, KM_SLEEP);
		strcpy(xfs_etest_fsname[i], mp->m_fsname);
		xfs_error_test_active++;
		return 0;
		}
		}
		@@ -137,6 +139,7 @@ xfs_errortag_clearall(xfs_mount_t *mp, int loud)
		xfs_etest_fsid[i] = 0LL;
		kmem_free(xfs_etest_fsname[i]);
		xfs_etest_fsname[i] = NULL;
		xfs_error_test_active--;
		}
		}

fs/xfs/xfs_error.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -127,13 +127,14 @@ extern void xfs_corruption_error(const char *tag, int level,
		#define XFS_RANDOM_BMAPIFORMAT XFS_RANDOM_DEFAULT

		#ifdef DEBUG
		extern int xfs_error_test_active;
		extern int xfs_error_test(int, int , char , int, char *, unsigned long);

		#define XFS_NUM_INJECT_ERROR 10
		#define XFS_TEST_ERROR(expr, mp, tag, rf) \
		((expr) \|\| \
		((expr) \|\| (xfs_error_test_active && \
		xfs_error_test((tag), (mp)->m_fixedfsid, "expr", __LINE__, __FILE__, \
		(rf)))
		(rf))))

		extern int xfs_errortag_add(int error_tag, xfs_mount_t *mp);
		extern int xfs_errortag_clearall(xfs_mount_t *mp, int loud);

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