On Tue, Apr 04, 2017 at 11:11:27PM +0100, Matthew Auld wrote:
> In its current form huge-pages through shmemfs are controlled at the
> super-block level, and are currently disabled by default, so to enable
> huge-pages for a shmem backed gem object we would need to re-mount the
> fs with the huge= argument, but for drm the mount is not user visible,
> so good luck with that. The other option is the global sysfs knob
> shmem_enabled which exposes the same huge= options, with the addition of
> DENY and FORCE.
>
> Neither option seems really workable, what we probably want is to able
> to control the use of huge-pages at the time of pinning the backing
> storage for a particular gem object, and only where it makes sense given
> the size of the object. One caveat is when we write into the page cache
> prior to pinning the backing storage. I played around with a bunch of
> ideas but in the end just settled with driver overridable huge option
> embedded in shmem_inode_info. Thoughts?
>
> Signed-off-by: Matthew Auld <[email protected]>
You need to Cc: mm folks and mailing lists for this. Ask
scripts/get_maintainers.pl for the full list please. Otherwise this can't
ever land (and we're looking at along time of bikeshedding anyway).
-Daniel
> ---
> include/linux/shmem_fs.h | 1 +
> mm/shmem.c | 10 ++++++++--
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> index a7d6bd2a918f..001be751420d 100644
> --- a/include/linux/shmem_fs.h
> +++ b/include/linux/shmem_fs.h
> @@ -21,6 +21,7 @@ struct shmem_inode_info {
> struct shared_policy policy; /* NUMA memory alloc policy */
> struct simple_xattrs xattrs; /* list of xattrs */
> struct inode vfs_inode;
> + bool huge; /* driver override shmem_huge */
> };
>
> struct shmem_sb_info {
> diff --git a/mm/shmem.c b/mm/shmem.c
> index e67d6ba4e98e..879a9e514afe 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1723,6 +1723,9 @@ static int shmem_getpage_gfp(struct inode *inode,
> pgoff_t index,
> /* shmem_symlink() */
> if (mapping->a_ops != &shmem_aops)
> goto alloc_nohuge;
> + /* driver override shmem_huge */
> + if (info->huge)
> + goto alloc_huge;
> if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
> goto alloc_nohuge;
> if (shmem_huge == SHMEM_HUGE_FORCE)
> @@ -2000,6 +2003,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
> unsigned long inflated_len;
> unsigned long inflated_addr;
> unsigned long inflated_offset;
> + struct shmem_inode_info *info = SHMEM_I(file_inode(file));
>
> if (len > TASK_SIZE)
> return -ENOMEM;
> @@ -2016,7 +2020,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
> if (addr > TASK_SIZE - len)
> return addr;
>
> - if (shmem_huge == SHMEM_HUGE_DENY)
> + if (!info->huge && shmem_huge == SHMEM_HUGE_DENY)
> return addr;
> if (len < HPAGE_PMD_SIZE)
> return addr;
> @@ -2030,7 +2034,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
> if (uaddr)
> return addr;
>
> - if (shmem_huge != SHMEM_HUGE_FORCE) {
> + if (!info->huge && shmem_huge != SHMEM_HUGE_FORCE) {
> struct super_block *sb;
>
> if (file) {
> @@ -4034,6 +4038,8 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
> loff_t i_size;
> pgoff_t off;
>
> + if (SHMEM_I(inode)->huge)
> + return true;
> if (shmem_huge == SHMEM_HUGE_FORCE)
> return true;
> if (shmem_huge == SHMEM_HUGE_DENY)
> --
> 2.9.3
>
> _______________________________________________
> Intel-gfx mailing list
> [email protected]
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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