[slurm-dev] Re: performance improvement for hostlist

[Hongjia Cao]

I wrote a simple test program test.c:

gcc
-I/home/hjcao/work/slurm/ /home/hjcao/work/build-slurm/src/api/libslurm.o 
-lpthread -ldl test.c

# ./a.out 
a.out: xmalloc usecs: 28530
a.out: malloc usecs: 5


the code:
==============================================================================================

#include <stdlib.h>
#include <string.h>

#include "src/common/xstring.h"
#include "src/common/xmalloc.h"
#include "src/common/macros.h"
#include "src/common/hostlist.h"
#include "src/common/timers.h"

#define COUNT 64
#define MAX_RANGES (64*1024)
struct _range {
                unsigned long lo, hi;
                        int width;
};


int main(int argc, char *argv[])
{
        char *ptr = NULL;
        int i;
        DEF_TIMERS;

        START_TIMER;
        for (i = 0; i < COUNT; i++) {
                ptr = xmalloc(MAX_RANGES * sizeof(struct _range));
                xfree(ptr);
        }
        END_TIMER;
        info("xmalloc usecs: %lld", delta_t);


        START_TIMER;
        for (i = 0; i < COUNT; i++) {
                ptr = malloc(MAX_RANGES * sizeof(struct _range));
                free(ptr);
        }
        END_TIMER;
        info("malloc usecs: %lld", delta_t);


        return 0;
}


在 2014-03-20四的 10:42 -0700，David Bigagli写道：
> Hi,
>     do you have any data comparing the performance of malloc() versus 
> xmalloc()? If you suspect the problem is in memset() it would be 
> interesting to see the performance of xmalloc() without it.
> 
> Is there any side effect of this patch since the memory is no longer 
> initialized to 0 if using malloc()?
> 
> On 03/19/2014 10:22 PM, Hongjia Cao wrote:
> > In commit 799a753be0c116a6117b0afa84f971fc2bdb9d87 the hostlist range
> > count was expanded and xmalloc/xfree is used to allocate memory for the
> > _range structure data. xmalloc is slow in setting the memory allocated
> > to 0: the size of _range structure will be 12 * 64 * 1024 = 768K bytes.
> > Replacing xmalloc/xfree with malloc/free improve the performance
> > notably.
> >
> > I find this when checking slowness of sinfo after upgrading from 2.6.0
> > to 2.6.6. The multithread patch (commit
> > 17449c066af69441b741110ef51fc2f534272871) does not help. Replacing
> > hostlist_push with hostlist_push_host (commit
> > 1b0b135f9579e253ddd5bf680d2ea70ad12f9bda) fixes the problem of sinfo,
> > but I think the root cause is in xmalloc.
> >
>