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authorSerapheim Dimitropoulos <serapheim@delphix.com>2019-10-18 10:24:28 -0700
committerBrian Behlendorf <behlendorf1@llnl.gov>2019-10-18 13:24:28 -0400
commit851eda356600167c080fe62d0a5726980c1c0b8a (patch)
tree750579d341856dd875d8b1964ebda52570c7b8ca /module
parentc9c9c1e213c15c0f0b94aebcea6b2268d7e8f52b (diff)
Update skc_obj_alloc for spl kmem caches that are backed by Linux
Currently, for certain sizes and classes of allocations we use SPL caches that are backed by caches in the Linux Slab allocator to reduce fragmentation and increase utilization of memory. The way things are implemented for these caches as of now though is that we don't keep any statistics of the allocations that we make from these caches. This patch enables the tracking of allocated objects in those SPL caches by making the trade-off of grabbing the cache lock at every object allocation and free to update the respective counter. Additionally, this patch makes those caches visible in the /proc/spl/kmem/slab special file. As a side note, enabling the specific counter for those caches enables SDB to create a more user-friendly interface than /proc/spl/kmem/slab that can also cross-reference data from slabinfo. Here is for example the output of one of those caches in SDB that outputs the name of the underlying Linux cache, the memory of SPL objects allocated in that cache, and the percentage of those objects compared to all the objects in it: ``` > spl_kmem_caches | filter obj.skc_name == "zio_buf_512" | pp name ... source total_memory util ----------- ... ----------------- ------------ ---- zio_buf_512 ... kmalloc-512[SLUB] 16.9MB 8 ``` Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #9474
Diffstat (limited to 'module')
-rw-r--r--module/os/linux/spl/spl-kmem-cache.c14
-rw-r--r--module/os/linux/spl/spl-proc.c28
2 files changed, 36 insertions, 6 deletions
diff --git a/module/os/linux/spl/spl-kmem-cache.c b/module/os/linux/spl/spl-kmem-cache.c
index 853cf33f0..865f2e2f8 100644
--- a/module/os/linux/spl/spl-kmem-cache.c
+++ b/module/os/linux/spl/spl-kmem-cache.c
@@ -1467,6 +1467,17 @@ spl_kmem_cache_alloc(spl_kmem_cache_t *skc, int flags)
obj = kmem_cache_alloc(slc, kmem_flags_convert(flags));
} while ((obj == NULL) && !(flags & KM_NOSLEEP));
+ if (obj != NULL) {
+ /*
+ * Even though we leave everything up to the
+ * underlying cache we still keep track of
+ * how many objects we've allocated in it for
+ * better debuggability.
+ */
+ spin_lock(&skc->skc_lock);
+ skc->skc_obj_alloc++;
+ spin_unlock(&skc->skc_lock);
+ }
goto ret;
}
@@ -1540,6 +1551,9 @@ spl_kmem_cache_free(spl_kmem_cache_t *skc, void *obj)
*/
if (skc->skc_flags & KMC_SLAB) {
kmem_cache_free(skc->skc_linux_cache, obj);
+ spin_lock(&skc->skc_lock);
+ skc->skc_obj_alloc--;
+ spin_unlock(&skc->skc_lock);
return;
}
diff --git a/module/os/linux/spl/spl-proc.c b/module/os/linux/spl/spl-proc.c
index a75bcc214..13eaa6301 100644
--- a/module/os/linux/spl/spl-proc.c
+++ b/module/os/linux/spl/spl-proc.c
@@ -437,11 +437,29 @@ slab_seq_show(struct seq_file *f, void *p)
ASSERT(skc->skc_magic == SKC_MAGIC);
- /*
- * Backed by Linux slab see /proc/slabinfo.
- */
- if (skc->skc_flags & KMC_SLAB)
+ if (skc->skc_flags & KMC_SLAB) {
+ /*
+ * This cache is backed by a generic Linux kmem cache which
+ * has its own accounting. For these caches we only track
+ * the number of active allocated objects that exist within
+ * the underlying Linux slabs. For the overall statistics of
+ * the underlying Linux cache please refer to /proc/slabinfo.
+ */
+ spin_lock(&skc->skc_lock);
+ seq_printf(f, "%-36s ", skc->skc_name);
+ seq_printf(f, "0x%05lx %9s %9lu %8s %8u "
+ "%5s %5s %5s %5s %5lu %5s %5s %5s %5s\n",
+ (long unsigned)skc->skc_flags,
+ "-",
+ (long unsigned)(skc->skc_obj_size * skc->skc_obj_alloc),
+ "-",
+ (unsigned)skc->skc_obj_size,
+ "-", "-", "-", "-",
+ (long unsigned)skc->skc_obj_alloc,
+ "-", "-", "-", "-");
+ spin_unlock(&skc->skc_lock);
return (0);
+ }
spin_lock(&skc->skc_lock);
seq_printf(f, "%-36s ", skc->skc_name);
@@ -461,9 +479,7 @@ slab_seq_show(struct seq_file *f, void *p)
(long unsigned)skc->skc_obj_deadlock,
(long unsigned)skc->skc_obj_emergency,
(long unsigned)skc->skc_obj_emergency_max);
-
spin_unlock(&skc->skc_lock);
-
return (0);
}