Re: [HACKERS] making use of large TLB pages

2002-09-29 Thread Bruce Momjian
Neil Conway wrote: Bruce Momjian [EMAIL PROTECTED] writes: Is TLB Linux-only? Well, the TLB is a feature of the CPU, so no. Many modern processors support large TLB pages in some fashion. However, the specific API for using large TLB pages differs between operating systems. The API

Re: [HACKERS] making use of large TLB pages

2002-09-29 Thread Neil Conway
Bruce Momjian [EMAIL PROTECTED] writes: OK, personally, I would like to see an actual speedup of PostgreSQL queries before I would apply such a OS-specific, version-specific patch. Don't be silly. A performance improvement is a performance improvement. According to your logic, using

Re: [HACKERS] making use of large TLB pages

2002-09-29 Thread Tom Lane
Neil Conway [EMAIL PROTECTED] writes: Bruce Momjian [EMAIL PROTECTED] writes: OK, personally, I would like to see an actual speedup of PostgreSQL queries before I would apply such a OS-specific, version-specific patch. Don't be silly. A performance improvement is a performance improvement.

Re: [HACKERS] making use of large TLB pages

2002-09-29 Thread Jonah H. Harris
, 2002 3:30 PM To: Tom Lane Cc: Neil Conway; PostgreSQL Hackers Subject: Re: [HACKERS] making use of large TLB pages Tom Lane wrote: Neil Conway [EMAIL PROTECTED] writes: Bruce Momjian [EMAIL PROTECTED] writes: OK, personally, I would like to see an actual speedup of PostgreSQL queries before I

Re: [HACKERS] making use of large TLB pages

2002-09-29 Thread Neil Conway
Jonah H. Harris [EMAIL PROTECTED] writes: I agree with Bruce and Tom. AFAIK Bruce and Tom (and myself) agree that this is a good idea, provided it makes a noticeable performance difference (and if it doesn't, it's not worth applying). AFAIK and in my experience I don't think it will be a

Re: [HACKERS] making use of large TLB pages

2002-09-28 Thread Tom Lane
Neil Conway [EMAIL PROTECTED] writes: If we used a key that would remain the same between runs of the postmaster, this should ensure that there isn't a possibility of two independant sets of backends operating on the same data dir. The most logical way to do this IMHO would be to just hash

Re: [HACKERS] making use of large TLB pages

2002-09-28 Thread Bruce Momjian
I haven't been following this thread. Can someone answer: Is TLB Linux-only? Why use it and non SysV memory? Is it a lot of code? --- Tom Lane wrote: Neil Conway [EMAIL PROTECTED] writes: If we

Re: [HACKERS] making use of large TLB pages

2002-09-28 Thread Neil Conway
Bruce Momjian [EMAIL PROTECTED] writes: Is TLB Linux-only? Well, the TLB is a feature of the CPU, so no. Many modern processors support large TLB pages in some fashion. However, the specific API for using large TLB pages differs between operating systems. The API I'm planning to

Re: [HACKERS] making use of large TLB pages

2002-09-27 Thread Neil Conway
Okay, I did some more research into this area. It looks like it will be feasible to use large TLB pages for PostgreSQL. Tom Lane [EMAIL PROTECTED] writes: It wasn't clear from your description whether large-TLB shmem segments even have IDs that one could use to determine whether the segment

Re: [HACKERS] making use of large TLB pages

2002-09-25 Thread Neil Conway
Tom Lane [EMAIL PROTECTED] writes: Neil Conway [EMAIL PROTECTED] writes: I'd like to enable PostgreSQL to use large TLB pages, if the OS and processor support them. Hmm ... it seems interesting, but I'm hesitant to do a lot of work to support something that's only available on one

Re: [HACKERS] making use of large TLB pages

2002-09-25 Thread Tom Lane
Neil Conway [EMAIL PROTECTED] writes: I think it's worthwhile implementing this, if possible. I wasn't objecting (I work for Red Hat, remember ;-)). I was just saying there's a limit to the messiness I think we should accept. The SysV API provides a reliable interlock to prevent this

[HACKERS] making use of large TLB pages

2002-09-24 Thread Neil Conway
Rohit Seth recently added support for the use of large TLB pages on Linux if the processor architecture supports them (I believe the SPARC, IA32, and IA64 have hugetlb support, more archs will probably be added). The patch was merged into Linux 2.5.36, so it will more than likely be in Linux 2.6.

Re: [HACKERS] making use of large TLB pages

2002-09-24 Thread Tom Lane
Neil Conway [EMAIL PROTECTED] writes: I'd like to enable PostgreSQL to use large TLB pages, if the OS and processor support them. Hmm ... it seems interesting, but I'm hesitant to do a lot of work to support something that's only available on one hardware-and-OS combination. (If we were