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Fixed several problems of the prefetching code:

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* Did claim to have reserved pages when calling vm_page_allocate_page(), but
  didn't have any (copy&paste bug). We cannot use it without reserved pages,
  as we need to call vm_page_allocate_page() with a cache locked.
* No longer use low_resource_state() to determine whether to precache or not,
  but use the new vm_page_num_used_pages() instead.
* Also don't (try to) precache when the cache already has more than 2/3 of its
  pages to safe some unnecessary work.
* The size to precache was limited to the file size incorrectly.
* When precaching failed, the cache reference was not released.
* The precaching started one page too late, causing bug #3835.
* Reenabled precaching.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@30515 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler
2009-04-30 15:53:41 +00:00
parent 2d8073a9dc
commit d5ad762913
2 changed files with 20 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/system/kernel/cache/file_cache.cpp
Vendored
+19 -14
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@@ -164,17 +164,16 @@ PrecacheIO::Start()
uint32 vecCount = 0;
uint32 i = 0;
for (size_t pos = 0; pos < fSize; pos += B_PAGE_SIZE) {
vm_page* page = fPages[i++] = vm_page_allocate_page(
PAGE_STATE_FREE, true);
vm_page* page = vm_page_allocate_page(PAGE_STATE_FREE, true);
if (page == NULL)
break;
fBusyConditions[i - 1].Publish(page, "page");
fBusyConditions[i].Publish(page, "page");
fCache->InsertPage(page, fOffset + pos);
add_to_iovec(fVecs, vecCount, fPageCount,
page->physical_page_number * B_PAGE_SIZE, B_PAGE_SIZE);
fPages[i++] = page;
}
if (i != fPageCount) {
@@ -903,10 +902,8 @@ file_cache_control(const char *subsystem, uint32 function, void *buffer,
extern "C" void
cache_prefetch_vnode(struct vnode *vnode, off_t offset, size_t size)
{
if (low_resource_state(B_KERNEL_RESOURCE_PAGES) != B_NO_LOW_RESOURCE) {
// don't do anything if we don't have the resources left
if (size == 0)
return;
}
vm_cache *cache;
if (vfs_get_vnode_cache(vnode, &cache, false) != B_OK)
@@ -915,12 +912,17 @@ cache_prefetch_vnode(struct vnode *vnode, off_t offset, size_t size)
file_cache_ref *ref = ((VMVnodeCache*)cache)->FileCacheRef();
off_t fileSize = cache->virtual_end;
if (offset >= fileSize) {
if (offset + size > fileSize)
size = fileSize - offset;
size_t reservePages = size / B_PAGE_SIZE;
// Don't do anything if we don't have the resources left, or the cache
// already contains more than 2/3 of its pages
if (offset >= fileSize || vm_page_num_unused_pages() < 2 * reservePages
|| 3 * cache->page_count > 2 * fileSize / B_PAGE_SIZE) {
cache->ReleaseRef();
return;
}
if (offset + size > fileSize)
size = offset - fileSize;
// "offset" and "size" are always aligned to B_PAGE_SIZE,
offset &= ~(B_PAGE_SIZE - 1);
@@ -929,7 +931,9 @@ cache_prefetch_vnode(struct vnode *vnode, off_t offset, size_t size)
size_t bytesToRead = 0;
off_t lastOffset = offset;
AutoLocker<VMCache> locker(cache);
vm_page_reserve_pages(reservePages);
cache->Lock();
while (true) {
// check if this page is already in memory
@@ -950,7 +954,7 @@ cache_prefetch_vnode(struct vnode *vnode, off_t offset, size_t size)
= new(std::nothrow) PrecacheIO(ref, lastOffset, bytesToRead);
if (io == NULL || io->Init() != B_OK || io->Start() != B_OK) {
delete io;
return;
break;
}
bytesToRead = 0;
@@ -961,10 +965,11 @@ cache_prefetch_vnode(struct vnode *vnode, off_t offset, size_t size)
break;
}
lastOffset = offset + B_PAGE_SIZE;
lastOffset = offset;
}
cache->ReleaseRefLocked();
cache->ReleaseRefAndUnlock();
vm_page_unreserve_pages(reservePages);
}