OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

squashfs: make use of local lock in multi_cpu decompressor 

Currently, the squashfs multi_cpu decompressor makes use of
get_cpu_ptr()/put_cpu_ptr(), which unconditionally disable preemption
during decompression.

Because the workload is distributed across CPUs, all CPUs can observe a
very high wakeup latency, which has been seen to be as much as 8000us.

Convert this decompressor to make use of a local lock, which will allow
execution of the decompressor with preemption-enabled, but also ensure
concurrent accesses to the percpu compressor data on the local CPU will
be serialized.

Cc: stable-rt@vger.kernel.org
Reported-by: Alexander Stein <alexander.stein@systec-electronic.com>
Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
This commit is contained in:
Julia Cartwright 2018-05-07 08:58:57 -05:00 committed by Alibek Omarov
parent bc7cc87312
commit d04a7ec191
1 changed files with 12 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
fs/squashfs/decompressor_multi_percpu.c
View File

@ -8,6 +8,7 @@
#include <linux/slab.h>
#include <linux/percpu.h>
#include <linux/buffer_head.h>
#include <linux/locallock.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
@ -23,6 +24,8 @@ struct squashfs_stream {
void *stream;
};
static DEFINE_LOCAL_IRQ_LOCK(stream_lock);
void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
void *comp_opts)
{
@ -77,10 +80,15 @@ int squashfs_decompress(struct squashfs_sb_info *msblk, struct buffer_head **bh,
{
struct squashfs_stream __percpu *percpu =
(struct squashfs_stream __percpu *) msblk->stream;
struct squashfs_stream *stream = get_cpu_ptr(percpu);
int res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
offset, length, output);
put_cpu_ptr(stream);
struct squashfs_stream *stream;
int res;
stream = get_locked_ptr(stream_lock, percpu);
res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
offset, length, output);
put_locked_ptr(stream_lock, stream);
if (res < 0)
ERROR("%s decompression failed, data probably corrupt\n",