[OpenAFS-devel] afs_osi_Sleep and afs_osi_Wakeup on Linux

[chas williams]

In message <OFEDF28ED3.7100E0A7-ON85256BCE.0051C9F7@in.ibm.com>,"Srikanth Vishwanathan" writes:
>I don't know is this is possible. But we don't drop GLOCK on other
>OSes. I guess we need to drop GLOCK because we call vmalloc() and
>schedule() in a loop in linux_alloc().

if this were the deadlock it would seem to imply that we were
waiting for afs to return memory so that vmalloc would be
able to finish.  since afs isnt very good about returning 
memory i cant see this as being the case.  do anyone know
why GLOCK is dropped?  what was the deadlock condition?

another thing about the allocator.  is it wise to choose
such a large max size when choosing to use kmalloc?  for
anything less than a pagesize, kmalloc is going to be
more efficient.  however, if your region is greater than
a page size (and you dont really need it to be contiguous)
you should probably be using vmalloc.  i know afs allocates
some 20000 chunks.  as an example look at this machine
running stock openafs:

size-131072(DMA)       0      0 131072    0    0   32
size-131072            2      2 131072    2    2   32
size-65536(DMA)        0      0  65536    0    0   16
size-65536             2      2  65536    2    2   16
size-32768(DMA)        0      0  32768    0    0    8
size-32768             4      4  32768    4    4    8
size-16384(DMA)        0      0  16384    0    0    4
size-16384             1      1  16384    1    1    4
size-8192(DMA)         0      0   8192    0    0    2
size-8192              6      6   8192    6    6    2

changing the kmalloc max size to 4096 yeilds what i would
consider better results:

size-131072(DMA)       0      0 131072    0    0   32
size-131072            0      0 131072    0    0   32
size-65536(DMA)        0      0  65536    0    0   16
size-65536             0      0  65536    0    0   16
size-32768(DMA)        0      0  32768    0    0    8
size-32768             0      0  32768    0    0    8
size-16384(DMA)        0      0  16384    0    0    4
size-16384             0      0  16384    0    0    4
size-8192(DMA)         0      0   8192    0    0    2
size-8192              2      3   8192    2    3    2

note how much the memory footprint has improved.