[Bug translator/6008] New: support larger on-memory buffer

["mhiramat at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

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.

-- 
           Summary: support larger on-memory buffer
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mhiramat at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=6008

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