Re: Re: Windows OpCache bug fix

Hi Eric, On Mon, Oct 5, 2015 at 9:49 PM, Eric Stenson <ericsten@microsoft.com> wrote: > >From: Dmitry Stogov [mailto:dmitry@zend.com] > > > >> On Thu, Oct 1, 2015 at 11:54 AM, Matt Ficken <themattficken@gmail.com> > >> wrote: > >> > >>> Pierre Joy wrote: > >>> And what wincache does. It is slower but the request is served. > >> > >> WinCache (file cache) if it can't reattach, creates a new shared mem > >> file > > > > I'm not sure how WinCache works, but opcache already implements most > > necessary functionality. > > Sorry for getting to the party late, but let me clarify what WinCache does: > > 1. For the opcode cache, if WinCache can't map to the same address, it > falls back to using process-local (heap) memory for the opcode arrays. > This is because the elements in the opcode arrays contain absolute > pointers, and we don't want to spend cycles (a) converting all pointers to > offsets when copying opcode arrays into shared memory, and then (b) > converting all offsets back to absolute addresses when copying the opcode > array back out of shared memory. WinCache simply gets the pointer to the > opcode array in shared memory and returns it, unmodified, to the PHP Core > for execution. > Opcache uses the same strategy,. > When WinCache falls back to process-local memory, it does NOT create a > second memory mapped segment, and does not chew additional cross-process > resources. > Opcahce but don't have a fall-back mechanism in case of inability to remap SHM into the same address space > 2. WinCache's file cache does not map to an identical address in all > processes. We simply map it to *any* address (using NULL for the suggested > address to MapViewOfFileEx), and then use relative offsets in the cache > structures for all entries in shared memory. > File-cache in opcache is a second level opcode cache. Instead of SHM (or in addition to SHM) we may store precompiled php scripts on disk. Thanks. Dmitry. > > 3. WinCache's user cache and session cache are similar to the file cache, > and do not have to map to the same address in all processes. Cache entries > use relative offsets to locate cache entries, and the values do not contain > absolute addresses. > > Finally, For PHP7, WinCache has removed its opcode cache. We assume that > Windows consumers of PHP7 will use Zend Opcache for opcode caching. > > > > Thx! > --E. >