Am 03.12.24 um 17:31 schrieb Thomas Hellström:
On Tue, 2024-12-03 at 17:20 +0100, Christian König wrote:
[SNIP]
@@ -453,9 +601,36 @@ int ttm_pool_alloc(struct ttm_pool
*pool,
struct ttm_tt *tt,
else
gfp_flags |= GFP_HIGHUSER;
- for (order = min_t(unsigned int, MAX_PAGE_ORDER,
__fls(num_pages));
- num_pages;
- order = min_t(unsigned int, order,
__fls(num_pages)))
{
+ order = min_t(unsigned int, MAX_PAGE_ORDER,
__fls(num_pages));
+
+ if (tt->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP) {
+ if (!tt->restore) {
+ gfp_t gfp = GFP_KERNEL |
__GFP_NOWARN;
+
+ if (ctx->gfp_retry_mayfail)
+ gfp |=
__GFP_RETRY_MAYFAIL;
+
+ tt->restore =
+ kvzalloc(struct_size(tt-
restore,
old_pages,
+
(size_t)1
<<
order), gfp);
+ if (!tt->restore)
+ return -ENOMEM;
+ } else if (ttm_pool_restore_valid(tt-
restore)) {
+ struct ttm_pool_tt_restore
*restore =
tt-
restore;
+
+ num_pages -= restore-
alloced_pages;
+ order = min_t(unsigned int, order,
__fls(num_pages));
+ pages += restore->alloced_pages;
+ r = ttm_pool_restore_tt(restore,
tt-
backup, ctx);
+ if (r)
+ return r;
+ caching = restore->caching_divide;
+ }
+
+ tt->restore->pool = pool;
+ }
Hui? Why is that part of the allocation function now?
At bare minimum I would expect that this is a new function.
It's because we now have partially backed up tts, so the
restore is
interleaved on a per-page basis, replacing the backup handles
with
page-pointers. I'll see if I can separate out at least the
initialization here.
Yeah, that kind of makes sense.
My expectation was just that we now have explicit
ttm_pool_swapout()
and
ttm_pool_swapin() functions.
I fully understand, although in the allocation step, that would
also
increase the memory pressure since we might momentarily have twice
the
bo-size allocated, if the shmem object was never swapped out, and
we
don't want to unnecessarily risc OOM at recover time, although that
should be a recoverable situation now. If the OOM receiver can free
up
system memory resources they can could potentially restart the
recover.
What I meant was more that we have ttm_pool_swapout() which does a
mix
of moving each page to a swap backend and freeing one by one.
And ttm_pool_swapin() which allocates a bit of memory (usually one
huge
page) and then copies the content back in from the swap backend.
Alternatively we could rename ttm_pool_alloc() into something like
ttm_pool_populate() and ttm_pool_free() into ttm_pool_unpopulate(),
but
those names are not very descriptive either.
It's just that we now do a bit more than just alloc and free in those
functions, so the naming doesn't really match that well any more.
So what about ttm_pool_alloc() and ttm_pool_recover/swapin(), both
pointing to the same code, but _alloc() asserts that the tt isn't
backed up?
That would give a clean interface at least.
More or less ok. I would just put figuring out the gfp flags and the
stuff inside the for (order... loop into separate functions. And then
remove the if (tt->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP) from the pool.
In other words you trigger the back restore by calling a different
function than the allocation one.
For a renaming change that touch all TTM drivers, I'd rather put that
as a last patch since getting acks for that from all TTM driver
maintainers seems like a hopeless undertaking.
Yeah the acks are not the problem, merging it through the xe tree would be.
Christian.
/Thomas
Christian.
/Thomas
