Messages in this thread | | | From | Alexander Shishkin <> | Subject | Re: [PATCH v1 03/11] perf: Allow for multiple ring buffers per event | Date | Mon, 10 Mar 2014 11:59:41 +0200 |
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Dave Hansen <dave.hansen@intel.com> writes:
> On 02/17/2014 06:33 AM, Peter Zijlstra wrote: >> Then write the PERF_RECORD_DATA structure into the normal ring-buffer >> location; set data_offset to point to the first page boundary, data_size >> to 1mb. >> >> Then frob things such that perf_mmap_to_page() for the next 1mb of pages >> points to your buffer pages and wipe the page-table entries. > > Wouldn't we have to teach a ton of code how to be IRQ safe for this to > work? Just step one: how do we go modifying page tables safely from an > interrupt? mm->page_table_lock is a plain non-irq spinlock.
Yes, this does look more than just tricky even if we move the bulk of interrupt code to an irq_work. Peter, are you quite sure this is what we want to do just for exporting trace buffers to userspace?
Regards, -- Alex
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