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Message-ID: <20130405093514.GA3848@quack.suse.cz>
Date: Fri, 5 Apr 2013 11:35:14 +0200
From: Jan Kara <jack@...e.cz>
To: Dmitry Monakhov <dmonakhov@...nvz.org>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: optimize ext4_end_io memory usage
On Mon 01-04-13 09:17:48, Dmitry Monakhov wrote:
> ext4_end_io->pages array has is used only for buffered writes and usless
> in case of DIO. This patch allow us to save 1K for each DIO request.
I have actually a more complete solution to this in my patch queue -
there isn't any need to reference pages from io_end after my patches.
Hopefully I'll be able to send things out later today...
Honza
> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> ---
> fs/ext4/ext4.h | 4 ++--
> fs/ext4/inode.c | 3 +--
> fs/ext4/page-io.c | 39 ++++++++++++++++++++++++++++++++-------
> 3 files changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 73f3e60..4c803af 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -219,7 +219,7 @@ typedef struct ext4_io_end {
> struct kiocb *iocb; /* iocb struct for AIO */
> int result; /* error value for AIO */
> int num_io_pages; /* for writepages() */
> - struct ext4_io_page *pages[MAX_IO_PAGES]; /* for writepages() */
> + struct ext4_io_page **pages; /* for writepages() */
> } ext4_io_end_t;
>
> struct ext4_io_submit {
> @@ -2622,7 +2622,7 @@ extern void ext4_add_complete_io(ext4_io_end_t *io_end);
> extern void ext4_exit_pageio(void);
> extern void ext4_ioend_shutdown(struct inode *);
> extern void ext4_free_io_end(ext4_io_end_t *io);
> -extern ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags);
> +extern ext4_io_end_t *ext4_init_io_end(struct inode *inode, int directio, gfp_t flags);
> extern void ext4_end_io_work(struct work_struct *work);
> extern void ext4_io_submit(struct ext4_io_submit *io);
> extern int ext4_bio_write_page(struct ext4_io_submit *io,
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index f455ac0..840a23e 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3162,12 +3162,11 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
> iocb->private = NULL;
> ext4_inode_aio_set(inode, NULL);
> if (!is_sync_kiocb(iocb)) {
> - ext4_io_end_t *io_end = ext4_init_io_end(inode, GFP_NOFS);
> + ext4_io_end_t *io_end = ext4_init_io_end(inode, 1, GFP_NOFS);
> if (!io_end) {
> ret = -ENOMEM;
> goto retake_lock;
> }
> - io_end->flag |= EXT4_IO_END_DIRECT;
> iocb->private = io_end;
> /*
> * we save the io structure for current async direct
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 047a6de..1b8ec50 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -29,16 +29,26 @@
> #include "xattr.h"
> #include "acl.h"
>
> -static struct kmem_cache *io_page_cachep, *io_end_cachep;
> +static struct kmem_cache *io_page_cachep, *io_pgvec_cachep, *io_end_cachep;
>
> int __init ext4_init_pageio(void)
> {
> io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT);
> if (io_page_cachep == NULL)
> return -ENOMEM;
> +
> + io_pgvec_cachep = kmem_cache_create("ext4_io_pgvec",
> + sizeof(struct ext4_io_page*)
> + * MAX_IO_PAGES,
> + 0, (SLAB_RECLAIM_ACCOUNT), NULL);
> + if (io_pgvec_cachep == NULL) {
> + kmem_cache_destroy(io_page_cachep);
> + return -ENOMEM;
> + }
> io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
> if (io_end_cachep == NULL) {
> kmem_cache_destroy(io_page_cachep);
> + kmem_cache_destroy(io_pgvec_cachep);
> return -ENOMEM;
> }
> return 0;
> @@ -47,6 +57,7 @@ int __init ext4_init_pageio(void)
> void ext4_exit_pageio(void)
> {
> kmem_cache_destroy(io_end_cachep);
> + kmem_cache_destroy(io_pgvec_cachep);
> kmem_cache_destroy(io_page_cachep);
> }
>
> @@ -83,12 +94,15 @@ void ext4_free_io_end(ext4_io_end_t *io)
> BUG_ON(!io);
> BUG_ON(!list_empty(&io->list));
> BUG_ON(io->flag & EXT4_IO_END_UNWRITTEN);
> + BUG_ON(io->num_io_pages && !io->pages);
>
> for (i = 0; i < io->num_io_pages; i++)
> put_io_page(io->pages[i]);
> io->num_io_pages = 0;
> if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count))
> wake_up_all(ext4_ioend_wq(io->inode));
> + if (io->pages)
> + kmem_cache_free(io_pgvec_cachep, io->pages);
> kmem_cache_free(io_end_cachep, io);
> }
>
> @@ -212,14 +226,25 @@ int ext4_flush_unwritten_io(struct inode *inode)
> return ret;
> }
>
> -ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
> +ext4_io_end_t *ext4_init_io_end(struct inode *inode, int directio, gfp_t flags)
> {
> ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
> - if (io) {
> - atomic_inc(&EXT4_I(inode)->i_ioend_count);
> - io->inode = inode;
> - INIT_LIST_HEAD(&io->list);
> +
> + if (!io)
> + return NULL;
> +
> + if (directio) {
> + io->flag = EXT4_IO_END_DIRECT;
> + } else {
> + io->pages = kmem_cache_zalloc(io_pgvec_cachep, flags);
> + if (!io->pages) {
> + kmem_cache_free(io_end_cachep, io);
> + return NULL;
> + }
> }
> + atomic_inc(&EXT4_I(inode)->i_ioend_count);
> + io->inode = inode;
> + INIT_LIST_HEAD(&io->list);
> return io;
> }
>
> @@ -327,7 +352,7 @@ static int io_submit_init(struct ext4_io_submit *io,
> int nvecs = bio_get_nr_vecs(bh->b_bdev);
> struct bio *bio;
>
> - io_end = ext4_init_io_end(inode, GFP_NOFS);
> + io_end = ext4_init_io_end(inode, 0, GFP_NOFS);
> if (!io_end)
> return -ENOMEM;
> bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
> --
> 1.7.1
>
> --
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--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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