Re: mmap'd file vs. swap
Poul-Henning Kamp wrote: > You can use regular VM by enabling the "malloc" storage method > and various people report good success with that. ... > Well, it's slightly more complex than that, we mmap with the > MAP_NOSYNC flag so it should be about a wash. Thanks. I wasn't familiar with MAP_NOSYNC since I am using Linux, which doesn't have it. In the mmap-based implementation, it looks like you have to implement malloc-like logic yourself, including thread-safety and defragmentation. Does the mmap-based storage have some advantage to normal malloc() implementations (e.g. glibc, jemalloc, TCMalloc) due to its domain-specific knowledge? Thanks, Brian ___ varnish-dev mailing list varnish-dev@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-dev
Re: mmap'd file vs. swap
In message <[EMAIL PROTECTED]>, "Brian Smith" writes: >My understanding is that Varnish uses a mmap'd file, but it doesn't re-use >the file's contents when it is restarted. Correct. > Why does Varnish use a mmap'd file >instead of just using regular virtual memory (swap) directly? For many small reasons, none of which are particularly good. You can use regular VM by enabling the "malloc" storage method and various people report good success with that. >I would think >that the operating system would be more eager to write the data to the >mmap'd file than it would be to write to swap; on a system where the hot >cache entries can be stored on disk, it would seem that the swap-based >method would be superior. Well, it's slightly more complex than that, we mmap with the MAP_NOSYNC flag so it should be about a wash. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ varnish-dev mailing list varnish-dev@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-dev
mmap'd file vs. swap
My understanding is that Varnish uses a mmap'd file, but it doesn't re-use the file's contents when it is restarted. Why does Varnish use a mmap'd file instead of just using regular virtual memory (swap) directly? I would think that the operating system would be more eager to write the data to the mmap'd file than it would be to write to swap; on a system where the hot cache entries can be stored on disk, it would seem that the swap-based method would be superior. (I ask because I am trying to decide which method to use for a back-end system, not to be critical of Varnish's design.) Thank you, Brian ___ varnish-dev mailing list varnish-dev@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-dev