Re: performance: use pread instead of lseek+read

Manfred Spraul <manfred@colorfullife.com> writes:
> Tom Lane wrote:
>> It seems unlikely to me that eliminating lseek on some platforms would
>> be worth the hassle of maintaining two code paths.  lseek is mighty
>> cheap as system calls go.
>>
> It was considered expensive enough to write a syscall avoidance layer
> that caches the file pointer and skips lseek if fpos==offset.

You're missing the point: that layer is mostly there to ensure that we
don't foul up the kernel's readahead recognition for sequential fetches.
It's nice that Linux doesn't care, but Linux is not the only platform
we worry about.

            regards, tom lane