Re: [PATCH] read-cache: make the index write buffer size 128K

>
> Jeff Hostetler <git@jeffhostetler.com> writes:
>
> > On 2/17/21 9:48 PM, Neeraj K. Singh via GitGitGadget wrote:
> >> From: Neeraj Singh <neerajsi@ntdev.microsoft.com>
> >> Writing an index 8K at a time invokes the OS filesystem and caching
> >> code
> >> very frequently, introducing noticeable overhead while writing large
> >> indexes. When experimenting with different write buffer sizes on Windows
> >> writing the Windows OS repo index (260MB), most of the benefit came by
> >> bumping the index write buffer size to 64K. I picked 128K to ensure that
> >> we're past the knee of the curve.
> >> With this change, the time under do_write_index for an index with 3M
> >> files goes from ~1.02s to ~0.72s.
> >
> > [...]
> >
> >>   -#define WRITE_BUFFER_SIZE 8192
> >> +#define WRITE_BUFFER_SIZE (128 * 1024)
> >>   static unsigned char write_buffer[WRITE_BUFFER_SIZE];
> >>   static unsigned long write_buffer_len;
> >
> > [...]
> >
> > Very nice.
>
> I wonder if we gain more by going say 4M buffer size or even larger?
>
> Is this something we can make the system auto-tune itself?  This is
> not about reading but writing, so we already have enough information
> to estimate how much we would need to write out.
>
> Thanks.
>