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[PATCH] splice: make the read-side do batched page lookups

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Use the new find_get_pages_contig() to potentially look up the entire
splice range in one single call. This speeds up generic_file_splice_read()
quite a bit.

Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-04-27 11:05:22 +02:00
parent ebf43500ef
commit eb20796bf6
1 changed files with 74 additions and 39 deletions
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91
fs/splice.c
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@ -279,7 +279,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
pgoff_t index, end_index;
loff_t isize;
size_t total_len;
int error;
int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
@ -307,24 +307,26 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
*/
error = 0;
total_len = 0;
for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {
unsigned int this_len;
if (!len)
break;
/*
* this_len is the max we'll use from this page
* Lookup the (hopefully) full range of pages we need.
*/
this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
find_page:
spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
/*
* lookup the page for this index
* If find_get_pages_contig() returned fewer pages than we needed,
* allocate the rest.
*/
index += spd.nr_pages;
while (spd.nr_pages < nr_pages) {
/*
* Page could be there, find_get_pages_contig() breaks on
* the first hole.
*/
page = find_get_page(mapping, index);
if (!page) {
/*
* page didn't exist, allocate one
* page didn't exist, allocate one.
*/
page = page_cache_alloc_cold(mapping);
if (!page)
@ -336,10 +338,36 @@ find_page:
page_cache_release(page);
break;
}
goto readpage;
/*
* add_to_page_cache() locks the page, unlock it
* to avoid convoluting the logic below even more.
*/
unlock_page(page);
}
pages[spd.nr_pages++] = page;
index++;
}
/*
* Now loop over the map and see if we need to start IO on any
* pages, fill in the partial map, etc.
*/
index = *ppos >> PAGE_CACHE_SHIFT;
nr_pages = spd.nr_pages;
spd.nr_pages = 0;
for (page_nr = 0; page_nr < nr_pages; page_nr++) {
unsigned int this_len;
if (!len)
break;
/*
* this_len is the max we'll use from this page
*/
this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
page = pages[page_nr];
/*
* If the page isn't uptodate, we may need to start io on it
*/
@ -360,7 +388,6 @@ find_page:
*/
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
break;
}
/*
@ -371,16 +398,20 @@ find_page:
goto fill_it;
}
readpage:
/*
* need to read in the page
*/
error = mapping->a_ops->readpage(in, page);
if (unlikely(error)) {
page_cache_release(page);
/*
* We really should re-lookup the page here,
* but it complicates things a lot. Instead
* lets just do what we already stored, and
* we'll get it the next time we are called.
*/
if (error == AOP_TRUNCATED_PAGE)
goto find_page;
error = 0;
break;
}
@ -389,10 +420,8 @@ readpage:
*/
isize = i_size_read(mapping->host);
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
if (unlikely(!isize || index > end_index)) {
page_cache_release(page);
if (unlikely(!isize || index > end_index))
break;
}
/*
* if this is the last page, see if we need to shrink
@ -400,27 +429,33 @@ readpage:
*/
if (end_index == index) {
loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
if (total_len + loff > isize) {
page_cache_release(page);
if (total_len + loff > isize)
break;
}
/*
* force quit after adding this page
*/
nr_pages = spd.nr_pages;
len = this_len;
this_len = min(this_len, loff);
loff = 0;
}
}
fill_it:
pages[spd.nr_pages] = page;
partial[spd.nr_pages].offset = loff;
partial[spd.nr_pages].len = this_len;
partial[page_nr].offset = loff;
partial[page_nr].len = this_len;
len -= this_len;
total_len += this_len;
loff = 0;
spd.nr_pages++;
index++;
}
/*
* Release any pages at the end, if we quit early. 'i' is how far
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)
page_cache_release(pages[page_nr++]);
if (spd.nr_pages)
return splice_to_pipe(pipe, &spd);