diff options
| -rw-r--r-- | src/file_handle_cache.erl | 38 |
1 files changed, 25 insertions, 13 deletions
diff --git a/src/file_handle_cache.erl b/src/file_handle_cache.erl index e539e0ac21..d0fd524fb8 100644 --- a/src/file_handle_cache.erl +++ b/src/file_handle_cache.erl @@ -359,7 +359,7 @@ read(Ref, Count) -> read_buffer_size = BufSz, hdl = Hdl, offset = Offset} - = tune_read_buffer_limit(Handle0), + = tune_read_buffer_limit(Handle0, Count), WantedCount = Count - BufRem, case prim_file_read(Hdl, lists:max([BufSz, WantedCount])) of {ok, Data} -> @@ -930,23 +930,35 @@ reset_read_buffer(Handle) -> read_buffer_rem = 0}. %% We come into this function whenever there's been a miss while -%% reading from the buffer - but note that when we seek we reset the -%% buffer, so the first read after a seek will always be a -%% miss. Therefore in that case don't take usage = 0 as meaning the -%% buffer was useless, we just haven't filled it yet! -tune_read_buffer_limit(Handle = #handle{read_buffer_usage = 0}) -> +%% reading from the buffer - but note that when we first start with a +%% new handle the usage will be 0. Therefore in that case don't take +%% it as meaning the buffer was useless, we just haven't done anything +%% yet! +tune_read_buffer_limit(Handle = #handle{read_buffer_usage = 0}, _Count) -> Handle; %% In this head we have been using the buffer but now tried to read %% outside it. So how did we do? If we used less than the size of the -%% buffer, make the new buffer that size. If we read 100% of what we -%% had, then double it for next time, up to the limit that was set -%% when we were created. -tune_read_buffer_limit(Handle = #handle{read_buffer_usage = Usg, +%% buffer, make the new buffer the size of what we used before, but +%% add one byte (so that next time we can distinguish between getting +%% the buffer size exactly right and actually wanting more). If we +%% read 100% of what we had, then double it for next time, up to the +%% limit that was set when we were created. +tune_read_buffer_limit(Handle = #handle{read_buffer = Buf, + read_buffer_usage = Usg, read_buffer_size = Sz, - read_buffer_size_limit = Lim}) -> + read_buffer_size_limit = Lim}, Count) -> + %% If the buffer is <<>> then we are in the first read after a + %% reset, the read_buffer_usage is the total usage from before the + %% reset. But otherwise we are in a read which read off the end of + %% the buffer, so really the size of this read should be included + %% in the usage. + TotalUsg = case Buf of + <<>> -> Usg; + _ -> Usg + Count + end, Handle#handle{read_buffer_usage = 0, - read_buffer_size = erlang:min(case Usg < Sz of - true -> Usg; + read_buffer_size = erlang:min(case TotalUsg < Sz of + true -> Usg + 1; false -> Usg * 2 end, Lim)}. |