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Clean up OS-specific ARC and kmem code

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OS-specific code (e.g. under `module/os/linux`) does not need to share
its code structure with any other operating systems.  In particular, the
ARC and kmem code need not be similar to the code in illumos, because we
won't be syncing this OS-specific code between operating systems.  For
example, if/when illumos support is added to the common repo, we would
add a file `module/os/illumos/zfs/arc_os.c` for the illumos versions of
this code.

Therefore, we can simplify the code in the OS-specific ARC and kmem
routines.

These changes do not impact system behavior, they are purely code
cleanup.  The changes are:

Arenas are not used on Linux or FreeBSD (they are always `NULL`), so
`heap_arena`, `zio_arena`, and `zio_alloc_arena` can be removed, along
with code that uses them.

In `arc_available_memory()`:
 * `desfree` is unused, remove it
 * rename `freemem` to avoid conflict with pre-existing `#define`
 * remove checks related to arenas
 * use units of bytes, rather than converting from bytes to pages and
   then back to bytes

`SPL_KMEM_CACHE_REAP` is unused, remove it.

`skc_reap` is unused, remove it.

The `count` argument to `spl_kmem_cache_reap_now()` is unused, remove
it.

`vmem_size()` and associated type and macros are unused, remove them.

In `arc_memory_throttle()`, use a less confusing variable name to store
the result of `arc_free_memory()`.

Reviewed-by: George Wilson <gwilson@delphix.com>
Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #10499
This commit is contained in:
Matthew Ahrens
2020-06-29 09:01:07 -07:00
committed by GitHub
parent 94a2dca6a0
commit 3c42c9ed84
11 changed files with 11 additions and 176 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/os/linux/zfs/arc_os.c
+7 -68
View File
@@ -126,74 +126,18 @@ arc_available_memory(void)
int64_t lowest = INT64_MAX;
free_memory_reason_t r = FMR_UNKNOWN;
int64_t n;
#ifdef freemem
#undef freemem
#endif
pgcnt_t needfree = btop(arc_need_free);
pgcnt_t lotsfree = btop(arc_sys_free);
pgcnt_t desfree = 0;
pgcnt_t freemem = btop(arc_free_memory());
if (needfree > 0) {
n = PAGESIZE * (-needfree);
if (n < lowest) {
lowest = n;
r = FMR_NEEDFREE;
}
if (arc_need_free > 0) {
lowest = -arc_need_free;
r = FMR_NEEDFREE;
}
/*
* check that we're out of range of the pageout scanner. It starts to
* schedule paging if freemem is less than lotsfree and needfree.
* lotsfree is the high-water mark for pageout, and needfree is the
* number of needed free pages. We add extra pages here to make sure
* the scanner doesn't start up while we're freeing memory.
*/
n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
n = arc_free_memory() - arc_sys_free - arc_need_free;
if (n < lowest) {
lowest = n;
r = FMR_LOTSFREE;
}
#if defined(_ILP32)
/*
* If we're on a 32-bit platform, it's possible that we'll exhaust the
* kernel heap space before we ever run out of available physical
* memory. Most checks of the size of the heap_area compare against
* tune.t_minarmem, which is the minimum available real memory that we
* can have in the system. However, this is generally fixed at 25 pages
* which is so low that it's useless. In this comparison, we seek to
* calculate the total heap-size, and reclaim if more than 3/4ths of the
* heap is allocated. (Or, in the calculation, if less than 1/4th is
* free)
*/
n = vmem_size(heap_arena, VMEM_FREE) -
(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
if (n < lowest) {
lowest = n;
r = FMR_HEAP_ARENA;
}
#endif
/*
* If zio data pages are being allocated out of a separate heap segment,
* then enforce that the size of available vmem for this arena remains
* above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
*
* Note that reducing the arc_zio_arena_free_shift keeps more virtual
* memory (in the zio_arena) free, which can avoid memory
* fragmentation issues.
*/
if (zio_arena != NULL) {
n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
(vmem_size(zio_arena, VMEM_ALLOC) >>
arc_zio_arena_free_shift);
if (n < lowest) {
lowest = n;
r = FMR_ZIO_ARENA;
}
}
last_free_memory = lowest;
last_free_reason = r;
@@ -317,14 +261,9 @@ SPL_SHRINKER_DECLARE(arc_shrinker,
int
arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
{
uint64_t available_memory = arc_free_memory();
uint64_t free_memory = arc_free_memory();
#if defined(_ILP32)
available_memory =
MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
#endif
if (available_memory > arc_all_memory() * arc_lotsfree_percent / 100)
if (free_memory > arc_all_memory() * arc_lotsfree_percent / 100)
return (0);
if (txg > spa->spa_lowmem_last_txg) {
@@ -338,7 +277,7 @@ arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
*/
if (current_is_kswapd()) {
if (spa->spa_lowmem_page_load >
MAX(arc_sys_free / 4, available_memory) / 4) {
MAX(arc_sys_free / 4, free_memory) / 4) {
DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
return (SET_ERROR(ERESTART));
}