On Wed, Nov 30, 2011 at 8:57 PM, Benny Halevy <bhalevy@xxxxxxxxxx> wrote:
> On 2011-12-03 06:56, Peng Tao wrote:
>> Asking for layout in pg_init will always make client ask for only 4KB
>> layout in every layoutget. This way, client drops the IO size information
>> that is meaningful for MDS in handing out layout.
>>
>> In stead, if layout is not find in cache, do not send layoutget
>> at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes
>> because that is where we know the real size of current IO. By telling the
>> real IO size to MDS, MDS will have a better chance to give proper layout.
>>
>> Signed-off-by: Peng Tao <peng_tao@xxxxxxx>
>> ---
>> Resend to fix patch title. Sorry for the noise...
>>
>> fs/nfs/blocklayout/blocklayout.c | 54 ++++++++++++++++++++++++++++++++++++-
>> 1 files changed, 52 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
>> index 48cfac3..fd585fe 100644
>> --- a/fs/nfs/blocklayout/blocklayout.c
>> +++ b/fs/nfs/blocklayout/blocklayout.c
>> @@ -39,6 +39,7 @@
>> #include <linux/prefetch.h>
>>
>> #include "blocklayout.h"
>> +#include "../internal.h"
>>
>> #define NFSDBG_FACILITY NFSDBG_PNFS_LD
>>
>> @@ -990,14 +991,63 @@ bl_clear_layoutdriver(struct nfs_server *server)
>> return 0;
>> }
>>
>> +/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
>
> Why is that?
> What do these arbitrary numbers represent?
> If these limits depend on some other system sizes they should reflect the dependency
> as part of their calculation.
What I wanted to add here is a limit to stop pg_test() (like object's
max_io_size) and 2MB is just an experience value...
Thanks,
Tao
>
> Benny
>
>> +#define PNFSBLK_MAXRSIZE (0x1<<22)
>> +#define PNFSBLK_MAXWSIZE (0x1<<21)
>> +static void
>> +bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
>> +{
>> + struct inode *ino = pgio->pg_inode;
>> + struct pnfs_layout_hdr *lo;
>> +
>> + BUG_ON(pgio->pg_lseg != NULL);
>> + spin_lock(&ino->i_lock);
>> + lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_KERNEL);
>> + if (!lo || test_bit(lo_fail_bit(IOMODE_READ), &lo->plh_flags)) {
>> + spin_unlock(&ino->i_lock);
>> + nfs_pageio_reset_read_mds(pgio);
>> + return;
>> + }
>> +
>> + pgio->pg_bsize = PNFSBLK_MAXRSIZE;
>> + pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
>> + req_offset(req),
>> + req->wb_bytes,
>> + IOMODE_READ);
>> + spin_unlock(&ino->i_lock);
>> +}
>> +
>> +static void
>> +bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
>> +{
>> + struct inode *ino = pgio->pg_inode;
>> + struct pnfs_layout_hdr *lo;
>> +
>> + BUG_ON(pgio->pg_lseg != NULL);
>> + spin_lock(&ino->i_lock);
>> + lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_NOFS);
>> + if (!lo || test_bit(lo_fail_bit(IOMODE_RW), &lo->plh_flags)) {
>> + spin_unlock(&ino->i_lock);
>> + nfs_pageio_reset_write_mds(pgio);
>> + return;
>> + }
>> +
>> + pgio->pg_bsize = PNFSBLK_MAXWSIZE;
>> + pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
>> + req_offset(req),
>> + req->wb_bytes,
>> + IOMODE_RW);
>> + spin_unlock(&ino->i_lock);
>> +}
>> +
>> static const struct nfs_pageio_ops bl_pg_read_ops = {
>> - .pg_init = pnfs_generic_pg_init_read,
>> + .pg_init = bl_pg_init_read,
>> .pg_test = pnfs_generic_pg_test,
>> .pg_doio = pnfs_generic_pg_readpages,
>> };
>>
>> static const struct nfs_pageio_ops bl_pg_write_ops = {
>> - .pg_init = pnfs_generic_pg_init_write,
>> + .pg_init = bl_pg_init_write,
>> .pg_test = pnfs_generic_pg_test,
>> .pg_doio = pnfs_generic_pg_writepages,
>> };
--
Thanks,
Tao
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