Messages in this thread | | | From | "Gilbert, Douglas" <> | Subject | Re: DMA page allocation | Date | Wed, 16 Jun 1999 17:13:56 -0400 |
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<P><FONT SIZE=2>Jaroslav wrote:</FONT> </P>
<P><FONT SIZE=2>> I'm really tired with the chronic problem of the linux kernel:</FONT> <BR><FONT SIZE=2>> DMA page allocation when the system memory size is far beyond 16MB.</FONT> <BR><FONT SIZE=2>> ALSA users (and OSS/Lite too) complain many times that the DMA buffer</FONT> <BR><FONT SIZE=2>> or a sound chip can't be allocated or it is too small, because the low</FONT> <BR><FONT SIZE=2>> 16MB memory is used with another things.</FONT> <BR><FONT SIZE=2>> [snip]</FONT> </P>
<P><FONT SIZE=2>This seems like a really good idea and will help the</FONT> <BR><FONT SIZE=2>SCSI sub-system which suffers from the same "GFP_DMA"</FONT> <BR><FONT SIZE=2>problem as the sound sub-system.</FONT> </P>
<P><FONT SIZE=2>The SCSI mid-level never knows when or if an ISA-based </FONT> <BR><FONT SIZE=2>adapter will be loaded as a module and hence makes _all_ </FONT> <BR><FONT SIZE=2>of its kmalloc() calls with the GFP_DMA flag. Most of the</FONT> <BR><FONT SIZE=2>oopses from the SCSI sub-system reported on this list</FONT> <BR><FONT SIZE=2>can be traced back to this problem. Patches are with</FONT> <BR><FONT SIZE=2>Alan to do something more sensible than memset() after</FONT> <BR><FONT SIZE=2>kmalloc() returns NULL, but this proposed change should</FONT> <BR><FONT SIZE=2>make that a very rare event.</FONT> </P>
<P><FONT SIZE=2>I will try it out and report how it goes.</FONT> </P>
<P><FONT SIZE=2>Doug Gilbert</FONT> </P>
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