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Subject[PATCH v2] squashfs: enhance parallel I/O
Date
Now squashfs have used for only one stream buffer for decompression
so it hurts parallel read performance so this patch supports
multiple decompressor to enhance performance parallel I/O.

Four 1G file dd read on KVM machine which has 2 CPU and 4G memory.

dd if=test/test1.dat of=/dev/null &
dd if=test/test2.dat of=/dev/null &
dd if=test/test3.dat of=/dev/null &
dd if=test/test4.dat of=/dev/null &

old : 1m39s -> new : 9s

* From v1
* Change comp_strm with decomp_strm - Phillip
* Change/add comments - Phillip

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
fs/squashfs/Kconfig | 13 +++
fs/squashfs/Makefile | 9 +-
fs/squashfs/decompressor_multi.c | 200 ++++++++++++++++++++++++++++++++++++++
3 files changed, 221 insertions(+), 1 deletion(-)
create mode 100644 fs/squashfs/decompressor_multi.c

diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
index c70111e..1c6d340 100644
--- a/fs/squashfs/Kconfig
+++ b/fs/squashfs/Kconfig
@@ -63,6 +63,19 @@ config SQUASHFS_LZO

If unsure, say N.

+config SQUASHFS_MULTI_DECOMPRESSOR
+ bool "Use multiple decompressors for handling parallel I/O"
+ depends on SQUASHFS
+ help
+ By default Squashfs uses a single decompressor but it gives
+ poor performance on parallel I/O workloads when using multiple CPU
+ machines due to waiting on decompressor availability.
+
+ If you have a parallel I/O workload and your system has enough memory,
+ using this option may improve overall I/O performance.
+
+ If unsure, say N.
+
config SQUASHFS_XZ
bool "Include support for XZ compressed file systems"
depends on SQUASHFS
diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
index c223c84..dfebc3b 100644
--- a/fs/squashfs/Makefile
+++ b/fs/squashfs/Makefile
@@ -4,8 +4,15 @@

obj-$(CONFIG_SQUASHFS) += squashfs.o
squashfs-y += block.o cache.o dir.o export.o file.o fragment.o id.o inode.o
-squashfs-y += namei.o super.o symlink.o decompressor.o decompressor_single.o
+squashfs-y += namei.o super.o symlink.o decompressor.o
+
squashfs-$(CONFIG_SQUASHFS_XATTR) += xattr.o xattr_id.o
squashfs-$(CONFIG_SQUASHFS_LZO) += lzo_wrapper.o
squashfs-$(CONFIG_SQUASHFS_XZ) += xz_wrapper.o
squashfs-$(CONFIG_SQUASHFS_ZLIB) += zlib_wrapper.o
+
+ifdef CONFIG_SQUASHFS_MULTI_DECOMPRESSOR
+ squashfs-y += decompressor_multi.o
+else
+ squashfs-y += decompressor_single.o
+endif
diff --git a/fs/squashfs/decompressor_multi.c b/fs/squashfs/decompressor_multi.c
new file mode 100644
index 0000000..462731d
--- /dev/null
+++ b/fs/squashfs/decompressor_multi.c
@@ -0,0 +1,200 @@
+/*
+ * Copyright (c) 2013
+ * Minchan Kim <minchan@kernel.org>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/buffer_head.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/cpumask.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "decompressor.h"
+#include "squashfs.h"
+
+/*
+ * This file implements multi-threaded decompression in the
+ * decompressor framework
+ */
+
+
+/*
+ * The reason that multiply two is that a CPU can request new I/O
+ * while it is waiting previous request.
+ */
+#define MAX_DECOMPRESSOR (num_online_cpus() * 2)
+
+
+int squashfs_max_decompressors(void)
+{
+ return MAX_DECOMPRESSOR;
+}
+
+
+struct squashfs_stream {
+ void *comp_opts;
+ struct list_head strm_list;
+ struct mutex mutex;
+ int avail_decomp;
+ wait_queue_head_t wait;
+};
+
+
+struct decomp_stream {
+ void *stream;
+ struct list_head list;
+};
+
+
+static void put_decomp_stream(struct decomp_stream *decomp_strm,
+ struct squashfs_stream *stream)
+{
+ mutex_lock(&stream->mutex);
+ list_add(&decomp_strm->list, &stream->strm_list);
+ mutex_unlock(&stream->mutex);
+ wake_up(&stream->wait);
+}
+
+void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
+ void *comp_opts)
+{
+ struct squashfs_stream *stream;
+ struct decomp_stream *decomp_strm = NULL;
+ int err = -ENOMEM;
+
+ stream = kzalloc(sizeof(*stream), GFP_KERNEL);
+ if (!stream)
+ goto out;
+
+ stream->comp_opts = comp_opts;
+ mutex_init(&stream->mutex);
+ INIT_LIST_HEAD(&stream->strm_list);
+ init_waitqueue_head(&stream->wait);
+
+ /*
+ * We should have a decompressor at least as default
+ * so if we fail to allocate new decompressor dynamically,
+ * we could always fall back to default decompressor and
+ * file system works.
+ */
+ decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
+ if (!decomp_strm)
+ goto out;
+
+ decomp_strm->stream = msblk->decompressor->init(msblk,
+ stream->comp_opts);
+ if (IS_ERR(decomp_strm->stream)) {
+ err = PTR_ERR(decomp_strm->stream);
+ goto out;
+ }
+
+ list_add(&decomp_strm->list, &stream->strm_list);
+ stream->avail_decomp = 1;
+ return stream;
+
+out:
+ kfree(decomp_strm);
+ kfree(stream);
+ return ERR_PTR(err);
+}
+
+
+void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)
+{
+ struct squashfs_stream *stream = msblk->stream;
+ if (stream) {
+ struct decomp_stream *decomp_strm;
+
+ while (!list_empty(&stream->strm_list)) {
+ decomp_strm = list_entry(stream->strm_list.prev,
+ struct decomp_stream, list);
+ list_del(&decomp_strm->list);
+ msblk->decompressor->free(decomp_strm->stream);
+ kfree(decomp_strm);
+ stream->avail_decomp--;
+ }
+ }
+
+ WARN_ON(stream->avail_decomp);
+ kfree(stream->comp_opts);
+ kfree(stream);
+}
+
+
+static struct decomp_stream *get_decomp_stream(struct squashfs_sb_info *msblk,
+ struct squashfs_stream *stream)
+{
+ struct decomp_stream *decomp_strm;
+
+ while (1) {
+ mutex_lock(&stream->mutex);
+
+ /* There is available decomp_stream */
+ if (!list_empty(&stream->strm_list)) {
+ decomp_strm = list_entry(stream->strm_list.prev,
+ struct decomp_stream, list);
+ list_del(&decomp_strm->list);
+ mutex_unlock(&stream->mutex);
+ break;
+ }
+
+ /*
+ * If there is no available decomp and already full,
+ * let's wait for releasing decomp from other users.
+ */
+ if (stream->avail_decomp >= MAX_DECOMPRESSOR)
+ goto wait;
+
+ /* Let's allocate new decomp */
+ decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
+ if (!decomp_strm)
+ goto wait;
+
+ decomp_strm->stream = msblk->decompressor->init(msblk,
+ stream->comp_opts);
+ if (IS_ERR(decomp_strm->stream)) {
+ kfree(decomp_strm);
+ goto wait;
+ }
+
+ stream->avail_decomp++;
+ WARN_ON(stream->avail_decomp > MAX_DECOMPRESSOR);
+
+ mutex_unlock(&stream->mutex);
+ break;
+wait:
+ /*
+ * If system memory is tough, let's for other's
+ * releasing instead of hurting VM because it could
+ * make page cache thrashing.
+ */
+ mutex_unlock(&stream->mutex);
+ wait_event(stream->wait,
+ !list_empty(&stream->strm_list));
+ }
+
+ return decomp_strm;
+}
+
+
+int squashfs_decompress(struct squashfs_sb_info *msblk,
+ void **buffer, struct buffer_head **bh, int b, int offset, int length,
+ int srclength, int pages)
+{
+ int res;
+ struct squashfs_stream *stream = msblk->stream;
+ struct decomp_stream *decomp_stream = get_decomp_stream(msblk, stream);
+ res = msblk->decompressor->decompress(msblk, decomp_stream->stream,
+ buffer, bh, b, offset, length, srclength, pages);
+ put_decomp_stream(decomp_stream, stream);
+ if (res < 0)
+ ERROR("%s decompression failed, data probably corrupt\n",
+ msblk->decompressor->name);
+ return res;
+}
--
1.7.9.5


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