wojtek at wojtek.tensor.gdynia.pl
Fri Aug 3 13:04:30 PDT 2007
>> -#define MAXPHYS (128 * 1024) /* max raw I/O transfer
>> size */
>> +#define MAXPHYS (512 * 1024) /* max raw I/O transfer
>> size */
>> both works for me and gives noticable speedup, when operating on big files
>> and when starting big apps or swapping.
> There are assumptions about the value of MAXPHYS all through the
> kernel. I doubt this patch works properly - it is something that
> should be fixed more completely though.
funny but THIS patch (MAXPHYS, not other) is working for me on 4 heavily
loaded servers for over a year with FreeBSD 6.2
while vm patch is running on my notebook for 2 days only, ok for now but
>> other question (swap_pager.c):
>> * SWB_NPAGES must be a power of 2. It may be set to 1, 2, 4, 8, or 16
>> * pages per allocation. We recommend you stick with the default of 8.
>> * The 16-page limit is due to the radix code (kern/subr_blist.c).
>> #ifndef MAX_PAGEOUT_CLUSTER
>> #define MAX_PAGEOUT_CLUSTER 16
>> can this be changed/fixed? 64-128 would be nicer...
> Why? i.e. what are the implications of this, good and bad?
for modern disk drives 64 kbytes is transferred below 1 milisecond, while
seek takes 8-10ms by average.
doing so small I/O is inefficient. something like 512kB (128 pages) looks
patched vm_fault make pageins faster, but not pageout. disks often does
write caching clustering pageouts anyway, but probably not that efficient.
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