squashfs: Enhance parallel I/O

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>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>

1 files changed, 200 insertions, 0 deletions

diff --git a/fs/squashfs/decompressor_multi.c b/fs/squashfs/decompressor_multi.c
new file mode 100644
index 000000000000..462731db5130
--- /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;
+}