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cache_io(): Reevaluate the memory situation periodically. Deciding at the 

beginning whether to pass the cache by really doesn't help when
reading/writing a huge amount of data, since a low memory situation is likely
to occur at some point during the operation. This should fix the main issue
of #3768.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@35299 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Ingo Weinhold 2010-01-26 17:22:46 +00:00
parent cff6e9e406
commit 7fa3e4e68a
1 changed files with 17 additions and 20 deletions
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37
src/system/kernel/cache/file_cache.cpp vendored
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@ -736,25 +736,6 @@ cache_io(void* _cacheRef, void* cookie, off_t offset, addr_t buffer,
if (size == 0)
return B_OK;
cache_func function;
if (doWrite) {
// in low memory situations, we bypass the cache beyond a
// certain I/O size
if (size >= BYPASS_IO_SIZE
&& low_resource_state(B_KERNEL_RESOURCE_PAGES)
!= B_NO_LOW_RESOURCE) {
function = write_to_file;
} else
function = write_to_cache;
} else {
if (size >= BYPASS_IO_SIZE
&& low_resource_state(B_KERNEL_RESOURCE_PAGES)
!= B_NO_LOW_RESOURCE) {
function = read_from_file;
} else
function = read_into_cache;
}
// "offset" and "lastOffset" are always aligned to B_PAGE_SIZE,
// the "last*" variables always point to the end of the last
// satisfied request part
@ -767,18 +748,33 @@ cache_io(void* _cacheRef, void* cookie, off_t offset, addr_t buffer,
size_t lastReservedPages = min_c(MAX_IO_VECS, (pageOffset + bytesLeft
+ B_PAGE_SIZE - 1) >> PAGE_SHIFT);
size_t reservePages = 0;
size_t pagesProcessed = 0;
cache_func function = NULL;
reserve_pages(ref, lastReservedPages, doWrite);
AutoLocker<VMCache> locker(cache);
while (bytesLeft > 0) {
// Periodically reevaluate the low memory situation and select the
// read/write hook accordingly
if (pagesProcessed % 32 == 0) {
if (size >= BYPASS_IO_SIZE
&& low_resource_state(B_KERNEL_RESOURCE_PAGES)
!= B_NO_LOW_RESOURCE) {
// In low memory situations we bypass the cache beyond a
// certain I/O size.
function = doWrite ? write_to_file : read_from_file;
} else
function = doWrite ? write_to_cache : read_into_cache;
}
// check if this page is already in memory
vm_page* page = cache->LookupPage(offset);
if (page != NULL) {
// The page may be busy - since we need to unlock the cache sometime
// in the near future, we need to satisfy the request of the pages
// we didn't get yet (to make sure no one else interferes in the
// mean time).
// meantime).
status_t status = satisfy_cache_io(ref, cookie, function, offset,
buffer, useBuffer, pageOffset, bytesLeft, reservePages,
lastOffset, lastBuffer, lastPageOffset, lastLeft,
@ -863,6 +859,7 @@ cache_io(void* _cacheRef, void* cookie, off_t offset, addr_t buffer,
bytesLeft -= bytesInPage;
pageOffset = 0;
offset += B_PAGE_SIZE;
pagesProcessed++;
if (buffer - lastBuffer + lastPageOffset >= kMaxChunkSize) {
status_t status = satisfy_cache_io(ref, cookie, function, offset,