The patch titled vfs: reduce stack usage by shrinking struct kiocb has been removed from the -mm tree. Its filename was vfs-reduce-stack-usage-by-shrinking-struct-kiocb.patch This patch was dropped because an updated version will be merged The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: vfs: reduce stack usage by shrinking struct kiocb From: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx> struct kiocb is placed on stack by, for example, do_sync_write(). Eventually it contributes to xfs writeout path's stack usage, among others. This is *the* path which causes 4k stack overflows on i386 with xfs. This patch trivially reorders fields of this structure, and makes some of them smaller. Reordering helps 64-bit architectures: int, void*, int, void* - bad, int, int, void*, void* - better. These fields are made smaller: ki_flags: long -> short: possible values are 0,1,2, so short is enough. ki_nr_segs: ulong -> uint: nobody uses 4 billion element writev's (and it would not work anyway) ki_cur_seg: same For 32bit x86, it makes this struct only 4 bytes smaller. This isn't much, but it helps not only xfs, but all filesystems. For 64-bit case savings are a bit more significant, as ulong -> uint actually makes a difference, and reordering of 64-bit fields eliminates some padding. Only compile tested. Observed stack reductions on 32 bits: -sock_recvmsg [vmlinux]: 196 -sock_sendmsg [vmlinux]: 196 +sock_recvmsg [vmlinux]: 192 +sock_sendmsg [vmlinux]: 192 -do_sync_write [vmlinux]: 140 -do_sync_read [vmlinux]: 140 +do_sync_write [vmlinux]: 136 +do_sync_read [vmlinux]: 136 -do_sync_readv_writev [vmlinux]: 132 +do_sync_readv_writev [vmlinux]: 128 Signed-off-by: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx> Cc: David Chinner <dgc@xxxxxxx> Cc: Benjamin LaHaise <bcrl@xxxxxxxxx> Cc: Eric Sandeen <sandeen@xxxxxxxxxxx> Cc: Zach Brown <zach.brown@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/aio.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff -puN include/linux/aio.h~vfs-reduce-stack-usage-by-shrinking-struct-kiocb include/linux/aio.h --- a/include/linux/aio.h~vfs-reduce-stack-usage-by-shrinking-struct-kiocb +++ a/include/linux/aio.h @@ -86,7 +86,8 @@ struct kioctx; */ struct kiocb { struct list_head ki_run_list; - unsigned long ki_flags; + unsigned short ki_flags; /* range: 0..2 */ + unsigned short ki_opcode; int ki_users; unsigned ki_key; /* id of this request */ @@ -102,23 +103,22 @@ struct kiocb { } ki_obj; __u64 ki_user_data; /* user's data for completion */ - wait_queue_t ki_wait; loff_t ki_pos; + wait_queue_t ki_wait; void *private; /* State that we remember to be able to restart/retry */ - unsigned short ki_opcode; + /*unsigned short ki_opcode; - moved up for denser packing */ size_t ki_nbytes; /* copy of iocb->aio_nbytes */ - char __user *ki_buf; /* remaining iocb->aio_buf */ size_t ki_left; /* remaining bytes */ + unsigned ki_nr_segs; + unsigned ki_cur_seg; struct iovec ki_inline_vec; /* inline vector */ + char __user *ki_buf; /* remaining iocb->aio_buf */ struct iovec *ki_iovec; - unsigned long ki_nr_segs; - unsigned long ki_cur_seg; struct list_head ki_list; /* the aio core uses this * for cancellation */ - /* * If the aio_resfd field of the userspace iocb is not zero, * this is the underlying file* to deliver event to. _ Patches currently in -mm which might be from vda.linux@xxxxxxxxxxxxxx are origin.patch vfs-reduce-stack-usage-by-shrinking-struct-kiocb.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html