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Implement combining scattered physical pages using seperate iovecs in

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PageWriteTransfer. This makes the transfer accept virtually contiguous pages,
where the offset is contiguous on either end of the current transfer, but where
the pages aren't physically contiguous. It will then add seperate iovecs for
these pages (32 at max right now). This reduces the number of IO requests
generated and allows for optimizations down the IO path (like in the physical to
virtual mapping case for example).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33526 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Michael Lotz 2009-10-11 16:52:19 +00:00
parent 303727515e
commit 7a4d60459e
1 changed files with 54 additions and 23 deletions
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77
src/system/kernel/vm/vm_page.cpp
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@ -1014,10 +1014,11 @@ private:
PageWriterRun* fRun;
struct VMCache* fCache;
off_t fOffset;
addr_t fPhysicalPageNumber;
uint32 fPageCount;
int32 fMaxPages;
status_t fStatus;
uint32 fVecCount;
iovec fVecs[32]; // TODO: make dynamic/configurable
};
@ -1152,10 +1153,13 @@ PageWriteTransfer::SetTo(PageWriterRun* run, vm_page* page, int32 maxPages)
fRun = run;
fCache = page->cache;
fOffset = page->cache_offset;
fPhysicalPageNumber = page->physical_page_number;
fPageCount = 1;
fMaxPages = maxPages;
fStatus = B_OK;
fVecs[0].iov_base = (void*)(page->physical_page_number << PAGE_SHIFT);
fVecs[0].iov_len = B_PAGE_SIZE;
fVecCount = 1;
}
@ -1166,23 +1170,53 @@ PageWriteTransfer::AddPage(vm_page* page)
|| (fMaxPages >= 0 && fPageCount >= (uint32)fMaxPages))
return false;
// TODO: this makes it required to be physically contiguous even though
// we could put physically disjoint pages into the same write using
// seperate iovecs for each page.
if ((page->physical_page_number != fPhysicalPageNumber + fPageCount
|| page->cache_offset != fOffset + fPageCount)
&& (page->physical_page_number != fPhysicalPageNumber - 1
|| page->cache_offset != fOffset - 1)) {
return false;
addr_t nextBase
= (addr_t)fVecs[fVecCount - 1].iov_base + fVecs[fVecCount - 1].iov_len;
if (page->physical_page_number << PAGE_SHIFT == nextBase
&& page->cache_offset == fOffset + fPageCount) {
// append to last iovec
fVecs[fVecCount - 1].iov_len += B_PAGE_SIZE;
fPageCount++;
return true;
}
if (page->physical_page_number < fPhysicalPageNumber)
fPhysicalPageNumber = page->physical_page_number;
if (page->cache_offset < fOffset)
nextBase = (addr_t)fVecs[0].iov_base - B_PAGE_SIZE;
if (page->physical_page_number << PAGE_SHIFT == nextBase
&& page->cache_offset == fOffset - 1) {
// prepend to first iovec and adjust offset
fVecs[0].iov_base = (void*)nextBase;
fVecs[0].iov_len += B_PAGE_SIZE;
fOffset = page->cache_offset;
fPageCount++;
return true;
}
fPageCount++;
return true;
if ((page->cache_offset == fOffset + fPageCount
|| page->cache_offset == fOffset - 1)
&& fVecCount < sizeof(fVecs) / sizeof(fVecs[0])) {
// not physically contiguous or not in the right order
uint32 vectorIndex;
if (page->cache_offset < fOffset) {
// we are pre-pending another vector, move the other vecs
for (uint32 i = fVecCount; i > 0; i--)
fVecs[i] = fVecs[i - 1];
fOffset = page->cache_offset;
vectorIndex = 0;
} else
vectorIndex = fVecCount;
fVecs[vectorIndex].iov_base
= (void*)(page->physical_page_number << PAGE_SHIFT);
fVecs[vectorIndex].iov_len = B_PAGE_SIZE;
fVecCount++;
fPageCount++;
return true;
}
return false;
}
@ -1192,16 +1226,12 @@ PageWriteTransfer::Schedule(uint32 flags)
off_t writeOffset = (off_t)fOffset << PAGE_SHIFT;
size_t writeLength = fPageCount << PAGE_SHIFT;
iovec vecs[1];
vecs->iov_base = (void*)(addr_t)(fPhysicalPageNumber << PAGE_SHIFT);
vecs->iov_len = writeLength;
if (fRun != NULL) {
return fCache->WriteAsync(writeOffset, vecs, 1, writeLength,
return fCache->WriteAsync(writeOffset, fVecs, fVecCount, writeLength,
flags | B_PHYSICAL_IO_REQUEST, this);
}
status_t status = fCache->Write(writeOffset, vecs, 1,
status_t status = fCache->Write(writeOffset, fVecs, fVecCount,
flags | B_PHYSICAL_IO_REQUEST, &writeLength);
SetStatus(status, writeLength);
@ -2202,6 +2232,7 @@ vm_page_allocate_page_run(int pageState, addr_t base, addr_t length)
break;
}
}
if (foundRun) {
// pull the pages out of the appropriate queues
for (i = 0; i < length; i++) {
@ -2210,11 +2241,11 @@ vm_page_allocate_page_run(int pageState, addr_t base, addr_t length)
set_page_state_nolock(&sPages[start + i], PAGE_STATE_BUSY);
sPages[start + i].usage_count = 2;
}
firstPage = &sPages[start];
break;
} else {
} else
start += i;
}
}
T(AllocatePageRun(length));