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Postings from May 2002
s/icebert/iceberg/ With apologies to Bert. PG > -----Original Message----- > From: Green, Paul [mailto:Paul.Green@stratus.com] > Sent: Monday, May 13, 2002 7:13 PM > To: 'Dave Mitchell'; Delta > Cc: perl5-porters@perl.org > Subject: RE: [ID 20020513.013] Perl bug -- split function > > > Dave Mitchell [mailto:davem@fdgroup.com] wonders, based on an > inquiry from > Delta, > > * Freeing the 1M scalars does take an *awfully* long time - > > is this Perl's fault or malloc()'s - or is that Life? > > > > Dave. > > I've worked with a number of different > operating-system-supplied storage > allocators over the years. They all make the basic assumption that the > caller is allocating a "reasonable" amount of storage and > holding onto it > for a "reasonable" length of time. When you have algorithms that > purposefully violate either of these "reasonable" > preconditions, you can > beat the performance of said allocator by writing your own. > But then, you > are off in the exciting world of dealing with all of the unreasonable > behavior requested by the universe of callers. > > The allocator we use on VOS allocates storage that is at least 64-byte > aligned. We allocate in units of 16 bytes. We have a 16-byte > overhead for > each block. We have to mask and unmask interrupts on every > allocation to > protect against program interrupts. We have to be careful in > case the heap > is damaged. Allocation and free performance is a goal, but is > outweighed by > correctness, reliability, nonfragmentation, and alignment goals. (By > aligning the data properly we optimize the performance of our > clients). > > The short answer is that 1M of anything is expensive. The > long answer is > that allocating storage is a nontrivial operation. If you > want to store a > million bytes efficiently, allocate a million-byte string and > use substr. > > Any good algorithms course and / or textbook goes into great > depth on these > subjects and should be read and studied by any software > engineer. This is > just the tip of the icebert. Go get a good book and read it, > or find a > local college and take their algorithms course. > > HTH > PG >Thread Previous | Thread Next