Bug 6008

Summary:	support larger on-memory buffer
Product:	systemtap	Reporter:	Masami Hiramatsu <mhiramat>
Component:	translator	Assignee:	Masami Hiramatsu <mhiramat>
Status:	RESOLVED FIXED
Severity:	normal
Priority:	P2
Version:	unspecified
Target Milestone:	---
Host:		Target:
Build:		Last reconfirmed:
Bug Depends on:	5645
Bug Blocks:
Attachments:	remove the size limitation of buffer relayfs patch: use vmalloc to allocate *page array extend size limitation of buffer to 4095MB

Description Masami Hiramatsu 2008-03-31 15:58:17 UTC

systemtap allows users to allocate more memories (ex. 2GB) for trace buffers
which can keep the trace data for a longer time on main memory.

Current trace buffer size is limited less than 64 MB per cpu even if we have a
plenty of memory (tens of GB) and a large memory space in kernel(especially
64bit arch). Therefore, we aren't able to log trace data for long enough.

Current limitation comes from relayfs which allocates an array of (struct page*)
for total allocating pages by kmalloc. However, usually, since the size of
kmalloc is limited, relayfs can not allocate the array if specified buffer size
is over (max_kmalloc_size/sizeof(struct page*))*page_size (=128KB/8B*4KB = 64MB
on x86-64). So, I think we can solve this by using vmalloc instead of kmalloc
when the array size is over one page_size.

Comment 1 Masami Hiramatsu 2008-04-08 20:33:26 UTC

Created attachment 2634 [details]
remove the size limitation of buffer

This patch removes current 64MB upper limitation from systemtap.

Comment 2 Masami Hiramatsu 2008-04-08 20:36:25 UTC

Created attachment 2648 [details]
relayfs patch: use vmalloc to allocate *page array

with this patch, relayfs uses vmalloc to allocate *page array if the array is
bigger than one page, otherwise, it uses kcalloc.

Comment 3 Masami Hiramatsu 2008-04-25 20:41:53 UTC

Created attachment 2719 [details]
extend size limitation of buffer to 4095MB

Since the buffer size is an "unsigned int" variable, we can't specify more than
4095 to -s option.

Comment 4 Masami Hiramatsu 2008-04-30 16:12:15 UTC

(In reply to comment #2)
> Created an attachment (id=2648)
> relayfs patch: use vmalloc to allocate *page array
> 
> with this patch, relayfs uses vmalloc to allocate *page array if the array is
> bigger than one page, otherwise, it uses kcalloc.
> 

this feature has been merged to linus tree(2.6.25-git15).

Comment 5 Masami Hiramatsu 2008-04-30 16:22:17 UTC

Patch Committed.