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fuse: realloc page array

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Writeback caching currently allocates requests with the maximum number of
possible pages, while the actual number of pages per request depends on a
couple of factors that cannot be determined when the request is allocated
(whether page is already under writeback, whether page is contiguous with
previous pages already added to a request).

This patch allows such requests to start with no page allocation (all pages
inline) and grow the page array on demand.

If the max_pages tunable remains the default value, then this will mean
just one allocation that is the same size as before.  If the tunable is
larger, then this adds at most 3 additional memory allocations (which is
generously compensated by the improved performance from the larger
request).

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi
2018-10-01 10:07:06 +02:00
parent 5da784cce4
commit e52a825048
3 changed files with 56 additions and 5 deletions
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49
fs/fuse/dev.c
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@@ -54,6 +54,18 @@ static void fuse_request_init(struct fuse_req *req, struct page **pages,
__set_bit(FR_PENDING, &req->flags);
}
static struct page **fuse_req_pages_alloc(unsigned int npages, gfp_t flags,
struct fuse_page_desc **desc)
{
struct page **pages;
pages = kzalloc(npages * (sizeof(struct page *) +
sizeof(struct fuse_page_desc)), flags);
*desc = (void *) pages + npages * sizeof(struct page *);
return pages;
}
static struct fuse_req *__fuse_request_alloc(unsigned npages, gfp_t flags)
{
struct fuse_req *req = kmem_cache_zalloc(fuse_req_cachep, flags);
@@ -63,13 +75,12 @@ static struct fuse_req *__fuse_request_alloc(unsigned npages, gfp_t flags)
WARN_ON(npages > FUSE_MAX_MAX_PAGES);
if (npages > FUSE_REQ_INLINE_PAGES) {
pages = kzalloc(npages * (sizeof(*pages) +
sizeof(*page_descs)), flags);
pages = fuse_req_pages_alloc(npages, flags,
&page_descs);
if (!pages) {
kmem_cache_free(fuse_req_cachep, req);
return NULL;
}
page_descs = (void *) pages + npages * sizeof(*pages);
} else if (npages) {
pages = req->inline_pages;
page_descs = req->inline_page_descs;
@@ -91,11 +102,41 @@ struct fuse_req *fuse_request_alloc_nofs(unsigned npages)
return __fuse_request_alloc(npages, GFP_NOFS);
}
void fuse_request_free(struct fuse_req *req)
static void fuse_req_pages_free(struct fuse_req *req)
{
if (req->pages != req->inline_pages)
kfree(req->pages);
}
bool fuse_req_realloc_pages(struct fuse_conn *fc, struct fuse_req *req,
gfp_t flags)
{
struct page **pages;
struct fuse_page_desc *page_descs;
unsigned int npages = min_t(unsigned int,
max_t(unsigned int, req->max_pages * 2,
FUSE_DEFAULT_MAX_PAGES_PER_REQ),
fc->max_pages);
WARN_ON(npages <= req->max_pages);
pages = fuse_req_pages_alloc(npages, flags, &page_descs);
if (!pages)
return false;
memcpy(pages, req->pages, sizeof(struct page *) * req->max_pages);
memcpy(page_descs, req->page_descs,
sizeof(struct fuse_page_desc) * req->max_pages);
fuse_req_pages_free(req);
req->pages = pages;
req->page_descs = page_descs;
req->max_pages = npages;
return true;
}
void fuse_request_free(struct fuse_req *req)
{
fuse_req_pages_free(req);
kmem_cache_free(fuse_req_cachep, req);
}